SHARKS AND RAYS (CHONDRICHTHYES ......SHARKS AND RAYS (CHONDRICHTHYES, ELASMOBRANCHII) FROM THE LATE MIOCENE GATUN FORMATION OF PANAMA CATALINA PIMIENTO,1,2,3 GERARDO GONZA´LEZ-BARBA,4

SHARKS AND RAYS (CHONDRICHTHYES, ELASMOBRANCHII) FROM THELATE MIOCENE GATUN FORMATION OF PANAMA

CATALINA PIMIENTO,1,2,3 GERARDO GONZALEZ-BARBA,4 DANA J. EHRET,5 AUSTIN J. W. HENDY,1,2

BRUCE J. MACFADDEN,1 AND CARLOS JARAMILLO2

1Florida Museum of Natural History, University of Florida, Gainesville, FL 32611, USA, ,[email protected].; ,[email protected].;,[email protected].; 2Smithsonian Tropical Research Institute, Center for Tropical Paleoecology and Archaeology, Box 2072, Panama,

Republic of Panama, ,[email protected].; 3Department of Biology, University of Florida, Gainesville, FL 32611, USA; 4Museo de Historia Natural,Area de Ciencias del Mar, La Paz, Universidad Autonoma de Baja California Sur, AP 23080, Mexico, ,[email protected].; and 5Alabama Museum

of Natural History, University of Alabama, Tuscaloosa, Alabama, 35487, USA, ,[email protected].

ABSTRACT—The late Miocene Gatun Formation of northern Panama contains a highly diverse and well sampled fossilmarine assemblage that occupied a shallow-water embayment close to a purported connection between the Pacific andAtlantic (Caribbean) oceans. However, the diverse chondrichthyan fauna has been poorly documented. Based on recentfield discoveries and further analysis of existing collections, the chondrichthyan fauna from this unit comprises at least 26taxa, of which four species are extinct today. The remaining portion of the total chondrichthyan biodiversity has affinitieswith modern taxa and is therefore comprised of long-lived species. Based on known records of the modern geographicdistribution range of the Gatun chondrichthyans, the fauna has mixed biogeographic affinities suggesting that around 10million yr ago, a connection likely occurred between the Pacific Ocean and the Caribbean Sea. Given the known habitatpreferences for modern chondrichthyans, the Gatun fauna was primarily adapted to shallow waters within the neritic zone.Finally, comparisons of Gatun dental measurements with other faunas suggest that many of the taxa have an abundance ofsmall individuals, in agreement with previous studies that proposed this area as a paleonursery habitat for the speciesCarcharocles megalodon.

INTRODUCTION

THE LATE Miocene Gatun Formation comprises fossiliferoussediments that crop out on the Caribbean coast of the

Isthmus of Panama, and contains a highly diverse macro- andmicrofossil fauna (e.g., Woodring, 1957–1982; Collins et al.,1996, 1999; Jackson and Budd, 1996; Jackson et al., 1999; Uhenet al., 2010; Hendy, 2013). Previous studies of the invertebratefauna from the Gatun Formation indicate this area was ashallow-water embayment that supported a neritic environment(Teranes et al., 1996). It has been postulated that this area was astrait connecting the Pacific Ocean and the Caribbean Sea(Coates and Obando, 1996), although subsequent workers havesuggested that any connection likely existed in a more distallocation (Collins et al., 1996, 1999; Teranes et al., 1996; Kirbyet al., 2008). Regardless, all these studies show that the Gatunmarine faunas existed during a time of active transoceanicinterchange and dispersal before the time of the final closure ofthe Central American Seaway (CAS).

It is generally accepted that the final closure of the CAS tookplace about 3 million yr ago (Duque-Caro, 1990; Coates et al.,1992, 2003, 2004; Coates and Obando, 1996; Bartoli et al.,2005). However, a number of recent studies suggest that theshoaling of the Isthmus began during the middle–late Eoceneand likely resulted in the final closure during the middleMiocene (Farris et al., 2011; Montes et al., 2012a, 2012b). Inany case, this closure was a key vicariant event for tropicalbiotic evolution (Cronin and Dowsett, 1996) that resulted in theseparation of the once continuous marine distribution, and anincrease of habitat and biogeographic complexity (e.g., Wood-ring, 1974; Rosen, 1975; Jackson and Budd, 1996; Aguilera etal., 2011).

Fossil chondrichthyans from Panama are poorly known in theliterature. The earliest record was reported by Blake (1862) who

noted three species from the Miocene deposits of Monkey Hill(present-day Colon). Of most significance to the current study,Gillette (1984) described the fossil chondrichthyans from theGatun Formation. Based on screenwashing of sediments at anow inaccessible (i.e., covered by urban development) locality,he described the diversity, ecology, and biogeography of 14chondrichthyan taxa. Most recently, Pimiento et al. (2010)studied the natural history of the species Carcharocles

megalodon from the Gatun Formation and proposed that theyused this area as a nursery habitat. Lastly, Pimiento et al. (2013)described the chondrichthyan fauna from the early MioceneCulebra Formation and studied their paleoenvironmental settingand paleobiogeography.

Over the past 20 yr, the Gatun Formation localities have beenextensively quarried to extract sediment for constructionprojects in the Colon region and contour surfaces for residentialdevelopments. These quarries have both uncovered freshoutcrops, but these are typically ephemeral (e.g., Gillette’slocality). Extraction activities have increased substantially inrecent years and numerous well-established outcrops are beingcompletely removed or covered by urban development. Wepredict that many of the critical outcrops of the Gatun Formationwill soon disappear. Given that the only systematic paleontologypaper on the chondrichthyans of the Gatun Formation waspublished 28 yr ago based on a single locality and collectionmethod, we consider it important to recover and document newspecimens from different sections before they are no longeravailable. Accordingly, we have collected and/or studied a totalof 800 specimens from 15 localities from the Gatun Formation.This material includes the original specimens described inGillette (1984), new specimens collected by our team, andadditional specimens in the Smithsonian National Museum ofNatural History, Washington, D.C.

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Journal of Paleontology, 87(5), 2013, p. 755–774

Copyright � 2013, The Paleontological Society

0022-3360/13/0087-755$03.00

DOI: 10.1666/12-117

The purpose of this report is to revise and update the fossilrecord of the chondrichthyan fauna from the Gatun Formation.Here, we review and describe all relevant known material.Furthermore, based on our study of the fossil specimens and theinformation available on extant related species, we evaluate thediversity, taxonomic composition, paleobiogeography, paleo-environment, and paleoecology of the chondrichthyan fauna ofthe Gatun Formation. Results of this study enhance ourunderstanding of the chondrichthyans of the ancient Neotropicsat a time when the Pacific Ocean and the Caribbean Sea wereconnected through Central America.

GEOLOGICAL SETTING

The fossil chondrichthyan teeth described in this paper werecollected from late Miocene marine sediments of the GatunFormation. This formation crops out in a broad area of northernPanama (Fig. 1) extending along the northern shore of LakeGatun, approximately 15 km northward to the Caribbean Sea,and approximately 50 km east and west of Colon City, withinthe Panama Canal structural basin. In the study area, the gentlydipping (58) Gatun Formation is thought to overlie unnamedCretaceous–Paleogene volcanic and volcaniclastic sediments orthe upper Oligocene sediments of the Caimito Formation(Woodring, 1957–1982; Coates et al., 1992; Coates, 1999)(Fig. 2).

The Gatun Formation, with a stratigraphic thickness of 500 m,consists of three informal members (Fig. 2) referred to as thelower, middle, and upper Gatun in most publications (e.g.,Woodring, 1957–1982; Coates, 1999). Of relevance to thisreport, most of the fossils collected during our study, and likelythose of Gillette (1984), occur within the lower member. Thelithology of these sediments consists of massive, gray-greenclayey siltstone and interbedded concretions. This member ofthe Gatun Formation is highly fossiliferous, with diversemolluscan assemblages (up to 259 genera and 359 species:Woodring, 1957–1982; Jackson et al., 1999). At some localitieswithin the Gatun Formation (e.g., Las Lomas, located ~12 kmsoutheast of Colon, locality 1 in Fig. 1.2) the highly fossiliferousnature of the sediments and weathering processes result inpavements of macrofossils (primarily bivalves and gastropods).Within this taphonomic context, marine vertebrate macrofossilsrecovered by surface prospecting consist mostly of chon-drichthyan teeth and ray tooth plates, as well as osteichthyanteeth (e.g., barracuda), turtle shell fragments, and raremammalian bones (Uhen et al., 2010). In addition, screen-washing of the siliciclastic matrix yielded rich microfossilassemblages, including benthic foraminifera (Collins, 1996),osteichthyan otoliths (Aguilera and Rodrigues de Aguilera,1999), and many small chondrichthyan taxa (Gillette, 1984).

Multiple lines of biostratigraphic evidence from the richmarine invertebrate fauna indicate that the Gatun Formation islate Miocene in age, spanning from about 11.8 to 8.4 million yrago (Coates, 1999; Jackson et al., 1999; Hendy, 2013; Fig. 2).Among other similarly diverse and relatively well-sampledmarine faunas in coastal regions of the western hemisphere,several faunas containing chondrichthyans bracket those of theGatun Formation: 1) older, early–middle Miocene assemblagesinclude: Shark tooth Hill, California (Pyenson et al., 2009);Pungo River, North Carolina (Ward and Bohaska, 2008);Agricola fauna, Florida (Morgan, 1994); Calvert fauna,Maryland (Tedford et al., 2004); Domo de Zaza, Cuba(MacPhee et al., 2003; Iturralde-Vinent et al., 1969); CantaureFormation, Venezuela (Aguilera, 2010); and Uscari Formation,Costa Rica (Pizarro, 1975; Laurito, 1999); 2) roughly contem-poraneous late Miocene assemblages include: St. Marys

Formation, Maryland (Tedford et al., 2004); Canımar Forma-tion, Cuba (Iturralde-Vinent, 1969); Grand Bay Formation ofCarriacou; Grenadines, Lesser Antilles (Donovan and Gunter,2001); and Rio Banano Formation, Costa Rica (Taylor, 1975;Laurito, 1999); 3) younger, early Pliocene assemblages include:Yorktown Formation, North Carolina (Ward and Bohaska,2008); Bone Valley, Florida (Morgan, 1994; Tedford et al.,2004); Pisco Formation (upper part), Peru (De Muizon andDeVries, 1985); and Cubagua Formation, Venezuela (Aguilera,2010).

With respect to the paleogeography, it has been postulatedthat the Gatun Formation was deposited within an archipelagicstrait connecting the Pacific Ocean and the Caribbean Sea(Coates and Obando, 1996). Subsequent workers indicated thatwaters had shoaled to the point the strait was restricted (Collinset al., 1996, 1999). Most recently, it has been suggested thatcontrary to an archipelago, a subaerial peninsula connected toNorth America existed during this time (Kirby and MacFadden,2005; Kirby et al., 2008). Regardless, all these studies show thata passageway existed between Central and South America, andit was located near to the deposition of sediments of the GatunFormation. Therefore, the Gatun faunas existed during a time ofactive transoceanic interchange and dispersal (Collins et al.,1996, 1999; Newkirk and Martin, 2009).

With regard to the paleoecology of the Gatun Formation,foraminifera (Collins, 1996), invertebrates (e.g., Coates andObando, 1996; Collins et al., 1996; Jackson et al., 1999; Hendy,2013) and fish otoliths (Aguilera and Rodrigues de Aguilera,1999) indicate a shallow-water marine shelf neritic environ-ment. A recent review of the paleoenvironments of the GatunFormation suggests that most of the formation accumulated indepths ranging from shallow subtidal to 50 m, although thesediments of the upper member accumulated in as much as 100m of water (Hendy, 2013). Studies of oxygen isotope ratiospreserved in mollusk shells from the Gatun Formation indicatethat it was deposited in a productive shallow-water embayment,and that salinity, annual temperature variations, relativeseasonality and productivity were different during the lateMiocene relative to those of today (Teranes et al., 1996).

REPOSITORIES, COLLECTING TECHNIQUES AND STATISTICAL ANALYSES

Specimens from the following vertebrate paleontologycollections were examined during this study and are abbreviatedin the text as follows: UF, Vertebrate Paleontology Collection,Florida Museum of Natural History, University of Florida,Gainesville, Florida; SMU, Shuler Museum of Paleontology,Southern Methodist University, Dallas, Texas; and USNM,Smithsonian Institution, National Museum of Natural History,Washington, D.C.

The UF material was collected by surface prospecting andscreenwashing between August 2007 and September 2011 from12 localities (Figs. 1, 2) by the Panama Canal Project (PCP)field team at the Center for Tropical Paleoecology andArchaeology of the Smithsonian Tropical Research Institute(STRI). This material is housed at UF and relevant data areavailable on the UF online database (http://www.flmnh.ufl.edu/databases/VP/intro.htm), where every fossil locality is coded(YPA, see caption Fig. 1.2). The screenwashing methodologyconsisted of washing approximately 500 kg of sediment fromthe three most fossiliferous localities (Las Lomas, Isla Payardiand San Judas; localities 1, 2, and 5 respectively in Figs. 1, 2).Samples were processed using standard screenwashing methods.We used sets of screens of 6, 1.5, 1, and 0.5 mm open mesh.Screenwashed matrix was picked for chondrichthyan teeth using

756 JOURNAL OF PALEONTOLOGY, V. 87, NO. 5, 2013

a magnifying glass for the coarser matrix, and a stereomicro-scope for the finest matrix.

In addition to the material collected in the field, we alsoborrowed specimens described by Gillette (1984), which are

housed in the SMU Vertebrate Paleontology collection. Thismaterial was collected in 1978 and 1979 from an exposure at asingle locality called ‘‘Sabanitas’’, now inaccessible (locality 15in Figs. 1, 2). His collection method consisted of screenwashing

FIGURE 1—Area of study. 1, location of Gatun Formation (shaded box) in northern Panama; 2, expanded geological map showing exposures of the GatunFormation and surrounding rock units (modified from Coates et al., 1992) including the 15 fossil localities collected during this study: 1, YPA017 Las Lomas:98210 15.66 00N, 79850011.34 00W; 2, YPA021 Isla Payardi: 9822057.18 00N, 79849016.50 00W; 3, YPA022 Cuatro Altos: 982007.08 00N, 79852058.80 00W; 4, YPA020Banco EE: 9817059.11 00N, 7985505.36 00W; 5, YPA032 San Judas: 982115.66 00N, 7985011.3274 00W; 6, YPA044 Sand Dollar Hill: 982102.628 00N, 79848035.532 00W;7, YPA030 Alborada: 9820027.024 00N, 7984900.804 00W; 8, YPA033 Texaco: 9820058.8474 00N, 79848047.304 00W; 9, YPA045 I.D.A.A.N.: 9820035.5194 00N,79848045 00W; 10, YPA 046 Third Set of Locks: 9816046.92 00N, 79854048.24 00W; 11, YPA043 Highway Extension 9820037.5 00N, 7984900.99 00W; 12, USNM: USGS58461, Gatun Dam: 9815046.08 00N, 79856026.16 00W; 13, USNM:USGS 8375, Gatun Dam: 9815053.2794 00N, 798550’54.4794 00W; 14, USNM: TU960, RefinerıaPanama: 9822056.64 00N, 79849016.32 00W; 15 Sabanitas (Gillette, 1984) 9820059.99 00N, 79847059.9994 00W. Lower Gatun localities include 1, 2, 5–9, 11, 14, 15;middle Gatun localities include 3, 10, 12, 13; and the upper Gatun locality is 4. YPA¼fossil locality code in the FLMNH database (http://www.flmnh.ufl.edu/databases/VP/intro.htm).

PIMIENTO ET AL.—LATE MIOCENE SHARKS AND RAYS FROM PANAMA 757

~900 kg of sediment using traditional wet-sieving methods (for

more detailed information see Gillette, 1984). Furthermore, we

borrowed specimens deposited at the USMN collected by R.

Stewart and W. P. Woodring (former USGS collections), and by

E. and H. Vokes (former Tulane University collections), both

between the 1950s and 1970s.

In total, 800 specimens were studied from 15 different

localities. Of the 634 specimens collected by our team (UF

material, screenwashing and surface prospecting, 12 localities)

we identified 24 taxa. Of the 161 specimens borrowed from the

Gillette’s (1984) work (SMU material, screenwashing, one

locality), we identified eight taxa, of which two were distinct

from our collecting efforts (Ginglymostoma delfortriei and

Sphyrna lewini). It is noteworthy that in contrast to our

identifications, Gillette (1984) reported 14 taxa. The difference

in number of taxa is due to the fact that some specimens were

missing from the SMU and in part reflects the redescription of

the originally collected material. Lastly, specimens borrowed

from USNM (three localities) contributed only three taxa. In

sum, we identified a total of 26 taxa for the Gatunchondrichthyan fauna.

Most of the material comes from a relatively limited thicknessof stratigraphy in the lower Gatun Formation, specifically LasLomas and San Judas (localities 1 and 2, respectively, in Fig. 2).These localities were among the most fossiliferous andaccessible of exposures in the formation, and have been exposedfor a significant period of time, resulting in considerableweathering of stratigraphic surfaces and concentration ofmacrofossils. Furthermore, a majority of specimens from thisstudy were collected by surface prospecting. However, somesmall-toothed taxa such as Ginglymostoma delfortriei, Rhizo-prionodon sp., Sphyrna lewini, Taeniura aff. grabata, Mobulamunkiana, Mobula thurstoni and Mobula hypostoma were onlyfound using screenwashing. Taxa with a broad range of toothsize such as Sphyrna sp., Carcharhinus sp., Negaprionbrevirostris, Aetobatus narinari, and Rhinoptera cf. steindach-neri were found with both screenwashing and surface prospect-ing techniques (Fig. 3).

A randomized species accumulation curve (Fig. 4) wasproduced to analyze the sampling effort (field days) in relationwith the species richness. This curve was created using thevegan package (Oksanen et al., 2010) of the R program (R-Development-Core-Team, 2012). The accumulation curveindicates that increased effort will unlikely result in finding asignificant number of additional taxa, and we therefore haveconfidently sampled most of the biodiversity of the Gatunchondrichthyan community.

SYSTEMATIC PALEONTOLOGY

The specimens were described following the terminology ofCappetta (1987, 2012), Herman et al. (1997, 1998, 1999, 2000),and Shimada (2002). The material was first identified by theauthors using comparative collections available at UF. Identi-fications were then verified by Dr. G. Hubbell using his privatecollection in Gainesville, FL. The geographic distribution ofeach taxon was retrieved from the literature and aided by usingthe Paleobiology Database (www.paleodb.org). All originalsources of data are cited herein. Macro-teeth were measuredwith calipers, whereas the micro-teeth were measured using theimages produced by the SEM (scanning electron microscope).Tooth measurements were compared when possible with aprevious work on the Neogene chondrichthyans of the PungoRiver Formation (middle Miocene) and the Yorktown Formation(early Pliocene) at Lee Creek Mine, North Carolina (Purdy etal., 2001), which are older and younger, respectively, than theGatun Formation. Shark teeth measurements are abbreviated asfollows: CH, tooth crown height; CW, tooth crown width; TL,total body length.

Class CHONDRICHTHYES Huxley, 1880Subclass ELASMOBRANCHII Bonaparte, 1838Order ORECTOLOBIFORMES Applegate, 1974Family GINGLYMOSTOMATIDAE Gill, 1872

Genus GINGLYMOSTOMA Muller and Henle, 1838GINGLYMOSTOMA DELFORTRIEI (Daimeries, 1889)

Figure 5.1

Description.—Ginglymostoma delfortriei tooth from the GatunFormation measures CH¼5.0 mm and W¼8.4 mm (Fig. 5.1). For adetailed description see Gillette (1984).

Material.—Two isolated teeth; indeterminate position (SMU76460 and SMU 76470).

Occurrence.—Lower Gatun locality 15 (Figs. 1, 2).Remarks.—In the Pungo River Formation, Purdy et al. (2001)

described one nurse shark tooth (Ginglymostoma sp.). This

FIGURE 2—Stratigraphy and sampling of the Gatun Formation. Fossillocalities are indicated by the numbers defined in Figure 1.2. The number ofsampling days (white) and elements recovered (black) from fossil localitiesare pooled for 50 m intervals of the composite stratigraphy of Hendy (2013).


specimen is very different from the G. delfortriei teeth studiedhere, with fewer cusps and a transverse groove. Ginglymostomadelfortriei is also reported in Venezuela and Costa Rica (Aguileraand Rodrigues de Aguilera, 2001; Laurito, 1999). Regarding theecology, extant species of the family Ginglymostomatidae (nursesharks) are subtropical and tropical, associated with corals, rockyreefs, sandy areas and mangroves; with a depth range of intertidalto 70 m (Compagno et al., 2005).

Order LAMNIFORMES Berg, 1958Family OTODONTIDAE Glikman, 1964

Genus CARCHAROCLES Jordan and Hannibal, 1923CARCHAROCLES MEGALODON (Agassiz, 1843)

Figure 5.2–5.4

1835 Carcharodon megalodon AGASSIZ, pl. 29, figs. 1–6.

Description.—Large size, triangular shape. Broad serratedcrown, lingual face convex, labial face flat, large neck; robust,thick, angled or U-shaped root with dispersed foramina (Fig. 5.2–5.4). Juvenile teeth of C. megalodon can have lateral cusplets(Fig. 5.4; Ward and Bonavia, 2001; Pimiento et al., 2010).Carcharocles megalodon differs from Carcharodon carchariasby having larger teeth with larger roots and finer, more regularand lobed serrations (Nyberg et al., 2006); lacking a labiolin-gually flattened crown (Purdy et al., 2001); and the presence of aneck. Carcharocles megalodon teeth from the Gatun Formationranges in size from CH¼11.2 to 72.3 mm and CW¼16.1 to 63.2mm.

Material.—Forty-nine (49) isolated teeth; upper anteriors: UF237898, UF 237949, UF 237954–237955, UF 242804, UF 247248

and USNM 960; lower anteriors: UF 237950, UF 237959, UF245995; upper laterals: UF 237914, UF 237951–237952, UF242802–242803, UF 245852, UF 245885–245886, UF 246033;lower lateral: UF 237953; upper posterior: UF 237957, UF245925, UF 246002; lower posterior: UF 237956, UF 245844, UF245996; indeterminate position: UF 237913, UF 237958, UF237960, UF 242801, UF 246001, UF 247250–247254, UF247256, UF 257576–257579, UF 266846, UF 266853–266858.

Occurrence.—Lower Gatun localities 1, 2, 7, 8, 14; middleGatun locality 10; upper Gatun locality 4 (Figs. 1, 2).

Remarks.—Teeth of C. megalodon (referred in Gillette, 1984 as

FIGURE 3—Late Miocene chondrichthyans from the Gatun Formation of Panama and proportional abundances (100%¼800 teeth) of each taxa using twodifferent collection techniques. Key: gray¼missing specimens from the SMU collection and therefore not available for comparison; *¼in agreement with ouridentification, but the taxonomy has been updated; **¼assigned to a different species; þ¼new records; †¼extinct taxa.

FIGURE 4—Species accumulation curve for the chondrichthyans of theGatun Formation. Shaded polygon represents confidence intervals.


Procarcharodon megalodon and in Purdy et al., 2001 asCarcharodon megalodon) can reach CH¼168 mm and TL isestimated to have been over 15 m (Gottfried et al., 1996). Teethfrom the Yorktown Formation are larger than teeth from theGatun Formation, ranging in size from CH¼60.0 to 150.0 mm(Purdy et al., 2001). Tooth morphology of C. megalodon changeswith the age. During the juvenile stage, teeth may or may notpresent lateral cusplets (for discussion see Applegate andEspinosa-Arrubarrena, 1996; Ward and Bonavia, 2001; Pimientoet al., 2010, 2013). UF 237914 presents lateral cusplets indicating

a juvenile stage (Fig. 5.4). The taxonomic assignment of thisspecies has been debated for nearly a century with numerouspossible interpretations. For discussion on our assignment here toCarcharocles, and not Carcharodon, Procarcharodon or Mega-

selachus, see Pimiento et al. (2010) and Ehret et al. (2012).Megatoothed sharks of the genus Carcharocles were common andwidely distributed in tropical to warm-temperate coastal habitats(Gottfried el al., 1996; Purdy, 1996). Carcharocles megalodon

was a cosmopolitan species (Cappetta, 1987; Purdy, 1996; Purdyet al., 2001). In the Neotropics, it has been reported both in the

FIGURE 5—Shark teeth from the late Miocene Gatun Formation, Panama. 1, †Ginglymostoma delfortriei (Daimeries, 1889), SMU 76470, indeterminateposition; 2–4, †Carcharocles megalodon (Agassiz, 1843): 2, UF 237950, largest anterior tooth; 3, UF 237959, smallest anterior tooth; 4, UF 237914, lateraltooth; 5–8, †Hemipristis serra (Agassiz, 1843): 5, UF 237941, largest upper tooth; 6, UF 237924, smallest upper tooth; 7, SMU 76467, smallest lower tooth; 8,UF 242806, largest complete lower tooth; 9, Galeocerdo cuvier (Peron and Lesueur, 1822), UF 237902, indeterminate position; 10, †Physogaleus contortus(Gibbes, 1849), UF 237908, indeterminate position; 11, Carcharhinus falciformis (Bibron, 1841 in Muller and Henle 1839–1841), UF 241817, upper tooth,square showing location of gap lacking of serrations; 12, Carcharhinus leucas (Valenciennes, 1839 in Muller and Henle 1839–1841), UF 241829, upper tooth;13, Carcharhinus obscurus (Lesueur, 1818), UF 242839, upper tooth; 14, Carcharhinus perezi (Poey, 1876), UF 242851, upper tooth; 15, Carcharhinusplumbeus (Nardo, 1827), UF 242860, upper tooth; 16, 17, Carcharhinus sp.: 16, UF 238004, upper tooth; 17, UF 241828, lower tooth; 18, Negaprion brevirostris(Poey, 1868), UF 241814, indeterminate position; 19, Rhizoprionodon sp. (Griffith and Smith, 1834), SMU 76475, indeterminate position; 20, Sphyrna lewini(Griffith and Smith, 1834), SMU 76458, upper tooth; 21, Sphyrna mokarran (Ruppell, 1837), UF 237912, upper tooth; 22, Sphyrna sp., UF 242868, upper tooth.Scale bar¼5 mm.


Caribbean and the Pacific (Iturralde-Vinent et al., 1996; Long-bottom, 1979; De Muizon and DeVries, 1985; Long, 1993;Laurito, 1999; Donovan and Gunter, 2001; Nieves-Rivera et al.,2003; Aguilera and Rodrigues de Aguilera, 2001; Portell et al.,2008). The species may have occurred in waters as deep as 300 m,although it is more frequently collected from sedimentsrepresenting neritic environments (e.g., Aguilera and Rodriguesde Aguilera, 2001). The relatively small size of many of the C.megalodon teeth from the Gatun Formation indicates a prepon-derance of juveniles, and suggests that this species used theshallow waters of northern Panama as a nursery area during thelate Miocene (Pimiento et al., 2010).

Order CARCHARHINIFORMES Compagno, 1977Family HEMIGALEIDAE Compagno, 1984

Genus HEMIPRISTIS Agassiz, 1843HEMIPRISTIS SERRA (Agassiz, 1843)

Figure 5.5–5.8

Description.—Upper teeth have distally curved crowns,oblique coarse serrations not continued to the apex, rectilinearmesial cutting edge, concave distal cutting edge with fewerserrations; root high and compressed with a lingual protuberanceforming a Z-shape. Upper teeth are generally broader than thecorresponding lowers (Fig. 5.5, 5.6). Lower teeth have unserrated,long, pointing and lingually inclined crowns; convex labial faces,small cusplets near the base, and bilobated roots with a lingualprotuberance (Fig. 5.7, 5.8). Upper teeth of H. serra differ fromthe genus Carcharhinus by having a distinctively smooth apexand oblique serrations; lower teeth differ from the genusCarcharias by having incomplete cutting edges on both mesialand distal side margins that are limited to approximately theapical third of the crown (Kent, 1994). In the Gatun Formationthis species varies greatly in size, from CH¼ 5.4 to 21.6 mm andCW¼ 5.2 to 29.0 mm.

Material.—One hundred twenty two (122) isolated teeth;uppers: UF 237919–237948, UF 241803–241808, UF 241835,UF 242810–242817, UF 245891–245892, UF 255909, UF255915–255916, UF 245926–245927, UF 245935–245942, UF245985, UF 245993, UF 245997–245998, UF 247260–247262,UF 247278–247281, UF 247286–247290, UF 247308–247309,UF 266771–266784, UF 266825, UF 266831, UF 266833, UF266837, USMN 22018 and USMN 8375; lowers: UF 241801–241802, UF 242805–242809, UF 242818, UF 245845–245846,UF 245854, UF 245856, UF 245861, UF 245863, UF 245874, UF245879, UF 245883–245884, UF 245889–245890, and SMU76467; indeterminate position: UF 266844, UF 266849–266850,and UF 267984.

Occurrence.—Lower Gatun localities 1, 2, 6, 8, 9, 15; middleGatun: localities 3, 10, 12; upper Gatun locality 4 (Figs. 1, 2).

Remarks.—Purdy et al. (2001) suggested that H. serra seems toincrease in size through its evolutionary history. The large size ofH. serra teeth suggests that this species reached total lengthsmuch greater than the living Hemipristis elongatus, perhaps up toTL¼6 m (Kent, 1994). Adult teeth of H. serra teeth from PungoRiver Formation range from CH¼14.1 to 29.1 mm and CW¼12.3to 35.5 mm (Purdy et al., 2001). In contrast, teeth from the GatunFormation are smaller than from the older Pungo RiverFormation, suggesting that the interpretation of increasing bodysize through time is not generally applicable for this species.Hemipristis serra is particularly abundant in neritic depositscontaining warm-water faunas and scarce in deposits with cold-adapted species (Cappetta, 1987). It is common in other Mioceneand Pliocene strata in Atlantic and Pacific basins of theNeotropics (Cappetta, 1987; Iturralde-Vinent et al., 1996; Laurito,1999; Purdy et al., 2001; MacPhee et al., 2003; Aguilera andRodrigues de Aguilera, 2001, 2004; Portell et al., 2008). Theextant H. elongatus is a tropical coastal shark that inhabits in-

shore and off-shore waters from 1 to 30 m depth (Compagno,1984).

Family CARCHARHINIDAE Jordan and Evermann, 1896Genus GALEOCERDO Muller and Henle, 1837

GALEOCERDO CUVIER (Peron and Lesueur, 1822)Figure 5.9

Description.—Large and robust teeth with slanted crowns;mesial edge rounded, with fine serrations at the base of crown,which is basally and apically straight, forming an obtuse angle;distal edge has a pronounced notch and have coarser serrations onthe heel and base; U-shaped root with no central foramen (Fig.5.9). Galeocerdo cuvier teeth are similar to those fromPhysogaleus aduncus, but have a broader and larger crown, anda more strongly convex mesial cutting edge. Galeocerdo cuvierteeth from the Gatun Formation range in size from CH¼7.4 to17.8 mm and CW¼14.4 to 24.5 mm. A transverse groove ispresent in the root of some, but not all teeth.

Material.—Twenty five (25) isolated teeth; indeterminateposition: UF 237901–237907, UF 241809–241812, UF 242819–242822, UF 245908, UF 245943–245944, UF 245982, UF247315, UF 266859, SMU 76456, SMU 76465, SMU 76466,and SMU 76475.

Occurrence.—Lower Gatun localities 1, 2, 8, 15 (Figs. 1, 2).Remarks.—Extant G. cuvier can reach up to TL¼7.5 m

(Compagno, 1984). Based on fossil teeth, it probably grew toless than half this length in the past (Kent, 1994). The teethcollected in the Yorktown Formation range from CH¼13.5 to 29.1mm and CW¼24.4 to 33.0 mm (Purdy et al., 2001), which arelarger than those found in the Gatun Formation. In the Neotropics,G. cuvier is reported in the Miocene of Venezuela and Brazil(Aguilera and Rodrigues de Aguilera, 2001; Reis, 2005). ExtantG. cuvier have a cosmopolitan distribution in coastal-pelagic,tropical and warm-temperature waters, with tolerance for a widerange of habitats at depths from intertidal waters to 140 m(Compagno, 1984, 1988).

Genus PHYSOGALEUS Cappetta, 1980PHYSOGALEUS CONTORTUS (Gibbes, 1849)

Figure 5.10

1848–1849 Galeocerdo contortus GIBBES, p. 193, pl. XXV,figs. 71–74.

Description.—Teeth are very similar to the genus Galeocerdowith finely serrated, long, thick and warped crowns; pronouncednotch, small serrations on heel of distal side; undulating marginand fine serrations on mesial edge; U-shaped root with prominentprotuberance on lingual face and transverse groove (Fig. 5.10).Physogaleus contortus differs from the genus Galeocerdo inhaving very prominent and bulging root with the deep notch, anda much more erect crown in lateral view (Leder, 2005).Physogaleus contortus teeth from the Gatun Formation rangefrom CH¼10.0 to 11.1 mm and CW¼12 to 15.5 mm.

Material.—Two teeth; indeterminate position: UF 237908 andUF 245984.

Occurrence.—Lower Gatun locality 1 (Figs. 1, 2).Remarks.—Teeth of P. contortus (referred in Gillette, 1984 and

Purdy et al., 2001 as Galeocerdo contortus) from the Pungo RiverFormation range from CH¼12.0 to 19.0 mm. Physogaleuscontortus typically occurs with Galeocerdo cuvier in Neogenelocalities along the east coast of the United States. Counts ofspecimens collected in Lee Creek Mine indicate that it is twice ascommon as Galeocerdo (Purdy et al., 2001). In contrast, only twospecimens have been identified relative to the more common G.cuvier in the Gatun Formation. Although uncommon in theNeotropics, it has been reported in Cuba (Iturralde-Vinent et al.,1996) and the genus Physogaleus is noted from Costa Rica


(Laurito, 1999). This species exhibits a cosmopolitan distributionduring the Miocene (Cappetta, 1987).

Genus CARCHARHINUS Blainville, 1816CARCHARHINUS FALCIFORMIS (Bibron, 1841

in Muller and Henle 1839–1841)Figure 5.11

Description.—Teeth triangular with narrow cusps; mesial edgestraight with a gap lacking of serrations at mid point (square inFig. 5.11), coarser serrations at the base, finer serrations at theapex; root with a transverse groove. They can have distal edgeswith angular notch perpendicular to the base. Carcharhinusfalciformis differs from other species of Carcharhinus by havinga gap lacking of serrations at the midpoint of the mesial cuttingedge. In the Gatun Formation, teeth range in size from CH¼5.1 to7.2 mm and CW¼4.9 to 6.4 mm.

Material.—Three isolated upper teeth: UF 241817, UF 270844,and UF 271113.

Occurrence.—Lower Gatun localities 1, 7 (Figs. 1, 2).Remarks.—Purdy et al. (2001) reported this species from the

middle Miocene Pungo River Formation. Their single toothmeasured CH¼14.2 mm and CW¼15.0 mm, which is twice aslarge as the largest Gatun specimen. Teeth in extant individualsvary in morphology, with some individuals not exhibiting the midpoint gap discussed above (Fig. 5.11) (Purdy et al., 2001). In theNeotropics, C. falciformis has been reported in the Miocene ofCosta Rica (Laurito, 1999). The extant C. falciformis is a largeepipelagic shark with a circumtropical distribution. It inhabitsnear shore, warm-shallow waters, from 18 to 500 m depth(Compagno, 1984; Purdy et al., 2001).

CARCHARHINUS LEUCAS (Valenciennes, 1839in Muller and Henle 1839–1841)

Figure 5.12

Description.—Teeth triangular; crowns finely serrated, serra-tions become progressively coarser near the base of crown, mesialedge straight or slightly convex with a shallow or absent notch,distal edge more concave with a shallow notch; U-shaped root.Some teeth have a well-developed transverse groove (Fig. 5.12).Lower teeth have thick crowns and cutting edges are finelyserrated (Purdy et al., 2001). Carcharhinus leucas differs fromother Carcharhinus species in having a more equilateral crownshape. Carcharhinus leucas from the Gatun Formation measurefrom CH¼7.5 to 10.7 mm and CW¼13.6 to 14.2 mm.

Material.—Fifteen (15) isolated teeth; uppers: UF 237979, UF237981, UF 237983, UF 237985,–237989, UF 241829–241830,and UF 242838; lowers: UF 237980, UF 237982, and UF 237984;indeterminate position: UF 247296.

Occurrence.—Lower Gatun locality 1; middle Gatun locality 3(Figs. 1, 2).

Remarks.—Teeth of C. leucas from Pungo River Formationrange from CH¼17.0 to 20.0 mm and CW¼16.0 to 22.0 mm.These probably belong to individuals that had a TL¼2 to 3 m(Purdy et al., 2001), and are larger than individuals from theGatun Formation. In the Neotropics, C. leucas has been reportedin Cuba and the Grenadines (Iturralde-Vinent et al., 1996;MacPhee et al., 2003; Portell et al., 2008). Extant individuals arelarge circumtropical epipelagic sharks, and are widespread inwarm oceans, rivers, and coastal lakes, in shallow (,30 m) depths(Compagno, 1984, 1988).

CARCHARHINUS OBSCURUS (Lesueur, 1818)Figure 5.13

Description.—Teeth have a broad crown; lingual surface flat,labial surface convex; thick root with a transverse groove. Upperteeth have basal crown serrations coarser than the apex, nearlyvertical distal cutting edge, mesial edge inclined distally,

concave, with convex apex (Fig. 5.13). Lower teeth have erectcrowns slightly broader in the apex in lingual view, and straightor moderately arched root lobes. Carcharhinus obscurus differsfrom other species of Carcharhinus by having coarser serrationsat the base of the crown. Carcharhinus obscurus from the GatunFormation measure from CH¼7.7 to 10.1 mm and CW¼11.2 to16.28 mm.

Material.—Six isolated teeth; uppers: UF 237915, UF 237917–237918, and UF 241818; lowers: UF 237916 and UF 242839.

Occurrence.—Lower Gatun locality 1 (Figs. 1, 2).Remarks.—Teeth of C. obscurus from Yorktown Formation

measure from CH¼17.0 to 22.0 mm and CW¼18.0 to 25.0 mm. Inextant individuals, sharks with corresponding tooth sizes have anestimated TL¼~3 m (Purdy et al., 2001), suggesting that C.obscurus from the Gatun Formation was smaller. In theNeotropics, C. obscurus has been reported in Cuba and theGrenadines (Iturralde-Vinent et al., 1996; MacPhee et al., 2003;Portell et al., 2008). Recent C. obscurus have a cosmopolitandistribution. They are common in coastal and pelagic, inshore andoffshore, warm-temperate and tropical, and continental andoceanic waters from intertidal to 400 m depth (Compagno, 1984).

CARCHARHINUS PEREZI (Poey, 1876)Figure 5.14

Description.—High teeth with narrow crown; distal edgeinclined, well-developed or rounded distal angular notch; mesialedge straight or slightly convex, medium to coarse serrations (Fig.5.14). Lower teeth with straight crowns, finely serrated cuttingedges and nearly straight root edges; however, in some cases,roots can vary mesially and distally to some extent. Some lateralteeth are slightly straight, making them difficult to differentiatefrom lower teeth. Carcharhinus perezi differs from otherCarcharhinus species by having a coarsely serrated crown, aninclined distal edge, and a straight mesial edge. Carcharhinusperezi from the Gatun Formation range from CH¼5.8 to 10.8 mmand CW¼10.6 to 16.9 mm.

Material.—Twenty four (24) isolated teeth; uppers: UF241819–241820, UF 241822, UF 242840–242842, UF 242844–242846, UF 242848–242853, UF 242855–242857; lowers: UF242845–242846; indeterminate position: UF 241821, UF 241843,UF 241847, and UF 241854.

Occurrence.—Lower Gatun locality 1; middle Gatun locality 3(Figs. 1, 2).

Remarks.—Teeth of C. perezi from Pungo River Formationmeasure from CH¼13.0 to 18.0 mm and CW¼13.0 to 22.0 mm,which corresponds to sharks of TL¼2 m (Purdy et al., 2001). Thissuggests that C. perezi from the Gatun Formation was representedby smaller individuals. In the Neotropics, C. perezi has beenreported in the Grenadines and Brazil (Reis, 2005; Portell et al.,2008). Extant sharks of this species inhabit tropical waters of theCaribbean Sea, and inshore of continental and insular shelvesdown to at least 30 m depth (Compagno, 1984).

CARCHARHINUS PLUMBEUS (Nardo, 1827)Figure 5.15

Description.—Narrow crown; moderate serrations on edges,distal edge inclined, mesial edge straight or slightly convex; thickroot (Fig. 5.15). Carcharhinus plumbeus may present a well-developed transverse groove or a central foramen and a U- or V-shaped root. Carcharhinus plumbeus teeth are very similar tothose from Carcharhinus obscurus, but C. plumbeus havenarrower and more elongated crowns with an apical convexityin cutting edges (Purdy et al., 2001). Carcharhinus plumbeusdiffers from Carcharhinus perezi in having finer serrations andapical convexity. Specimens from the Gatun Formation measurefrom CH¼6.8 to 10.6 mm and CW¼10.3 to 6.1 mm.

Material.—Five isolated teeth; uppers: UF 242858–242862.


Occurrence.—Lower Gatun locality 1 (Figs 1, 2).Remarks.—Teeth of C. plumbeus teeth from Pungo River

Formation measure from CH¼14.0 to 19.0 mm. Teeth of this sizecorrespond to sharks of TL¼2 m (Purdy et al., 2001), indicatingthat C. plumbeus from the Gatun Formation was represented bysmaller individuals. In the Neotropics, they have been reportedin the Miocene of Venezuela and Cuba (Iturralde-Vinent et al.,1996; Aguilera and Rodrigues de Aguilera, 2001; MacPhee etal., 2003). Extant C. plumbeus are cosmopolitan, coastal-pelagicsharks of warm temperate and tropical waters, found in insularand continental shelves and deep waters adjacent to them. Theyrange from intertidal waters to 280 m in depth (Compagno,1984).

CARCHARHINUS sp.Figure 5.16, 5.17

Description.—Upper teeth of the Carcharhinus sp. from theGatun Formation have triangular shape; straight crown in anteriorteeth and curved in laterals, flat labial face, slightly convexlingual face, serrated cutting edges, and cusps separated or notfrom heels. Roots can present a clear transverse groove in smallforms (Fig. 5.16). Lower teeth have narrower cusps, crown wellseparated from heel, cutting edges serrated, with a transversegroove (Fig. 5.17). Lower teeth of Carcharhinus sp. differ fromNegaprion brevirostris by having serrated cutting edges and fromthe genus Sphyrna by having a thinner root and the lack of anexpanded lingual heel. This genus is abundant in the GatunFormation with teeth ranging greatly in size, from CH¼1.9 to 12.9mm and CW¼4.1 to 17.6 mm.

Material.—Three hundred seventeen (317) isolated teeth;uppers: UF 237990–237999, UF 238001–238018, UF 238021–238025, UF 238032, UF 241823–241825, UF 241827, UF242825–242826, UF 242829, UF 242832, UF 242871; lowers:UF 237992, UF 237995, UF 237998–UF 237999, UF 241828, UF241831–241832, UF 242823–242824, UF 242827–242828, UF242830–242831, UF 242833, UF 242836, UF 242871; lateral:SMU 76475; indeterminate position: UF 238019, UF 241826, UF242834–242835, UF 242837, UF 245848–245851, UF 245853,UF 245855, UF 245857–245860, UF 245866–245873, UF245876–245878, UF 245880, UF 245887–245888, UF 245894–245907, UF 245910–245912, UF 245917–245921, UF 245928–245934, UF 245959–245981, UF 245987–245992, UF 245994,UF 246000, UF 247258, UF 247268–247277, UF 247282–247285, UF 247291, UF 247298–247299, UF 247307, UF247310–247314, UF 266791–266823, UF 266826–266827, UF266829–266830, UF 266832, UF 266834, UF 266835, UF266838, UF 266840–266843, UF 266848, UF 266851–266852,UF 267979, UF 267982–267983, SMU 76457–76459, SMU76463, SMU 76465, SMU 76469, SMU 76472–76475, andUSMN 58461.

Occurrence.—Lower Gatun localities 1, 2, 5–9, 11, 14, 15;middle Gatun localities 10, 12; upper Gatun locality 4 (Figs. 1, 2).

Remarks.—Much taxonomic confusion exists within thisgenus (Purdy et al., 2001). The identification of individualCarcharhinus species based solely on isolated teeth is extremelydifficult given the degree of similarity in tooth morphology.This problem is particularly acute in lower teeth, which are verysimilar among most species (Kent, 1994). Factors influencingvariation in tooth shape within the genus Carcharhinus include:variation among species, variation within a species, differenceswithin individuals of a species (Naylor and Marcus, 1994) andwithin a tooth row. Upper teeth of the genus Carcharhinus havebeen documented up to CH¼20 mm (Cappetta, 1987). Sharks ofthis genus are wide-ranging in tropical waters, with someranging in warm temperate waters. Most species are coastal anda few are oceanic. Some species are very common in coral reefs(Compagno, 1988).

Genus NEGAPRION Whitley, 1940NEGAPRION BREVIROSTRIS (Poey, 1868)

Figure 5.18

Description.—Teeth of N. brevirostris have a T-shape; narrowunserrated crown perpendicular to the root; and flat roots withtransverse groove. They can also have a slightly curved, inclinedcrown; lingual face flat and labial face slightly convex; elongatedroot lobes, and strongly obtuse basal root angle. Moderateontogenetic heterodonty is observed in this species with smallerspecimens lacking serrations on heels (Fig. 5.18) while largerindividuals exhibit them (Compagno, 1984; Purdy et al., 2001).Lower teeth of N. brevirostris differ from the genus Carcharhinusby not having serrations on the crown. Negaprion brevirostrisfrom the Gatun Formation measurements range from CH¼3.7 to13.7 mm and CW¼4.3 to 16.3 mm.

Material.—Ninety four (94) isolated teeth; indeterminateposition: UF 237961–237978, UF 241813–241816, UF 241833–241834, UF 242863–242867, UF 245847, UF 245864, UF245875, UF 245881–245882, UF 245893, UF 245913–245914,UF 245945–245951, UF 245983, UF 245986, UF 245999, UF247263–247264, UF 247267, UF 247288, UF 266785–266787,UF 266824, UF 266828, UF 266836, UF 266839, UF 266845, UF266847, SMU 76455, SMU 76458–76459, SMU 76465, SMU76469, and SMU 76474–76475.

Occurrence—Lower Gatun localities 1, 2, 5, 6, 8, 9, 15; middleGatun locality 10; upper Gatun locality 4 (Figs. 1, 2).

Remarks.—In the Miocene, this species is referred to asNegaprion eurybathrodon (e.g., Cappetta, 1987; Purdy et al.,2001). However, since the tooth morphology of the Gatunspecimens is not different from the modern lemon shark, weassign them to N. brevirostris. Cappetta (1987) established themaximum CH of for Negaprion to be 20 mm. Purdy et al. (2001)reported teeth in the Pungo River Formation, measuring fromCH¼14 to 21 mm and stated that in extant N. brevirostris teeth ofthis size are found in sharks of TL¼2.1 to 3 m, which is the sizerange for mature adults according to Compagno (1984). Thissuggests that most of the specimens assigned to N. brevirostris inthe Gatun Formation are juveniles. The lack of serrations on theheels of most of the specimens corroborates this hypothesis. In theNeotropics, N. brevirostris (¼N. eurybathrodon) has beenreported in the Miocene of Venezuela, Cuba and Ecuador(Iturralde-Vinent et al., 1996; (Aguilera and Rodrigues deAguilera, 2001; MacPhee et al., 2003; Longbottom, 1979). ExtantN. brevirostris inhabits tropical and temperate estuarine andintertidal through offshore (0–92 m) waters of the Atlantic and thePacific Ocean (Compagno, 1984; Kent, 1994).

Genus RHIZOPRIONODON Whitley, 1929RHIZOPRIONODON sp.

Figure 5.19

Description.—Rhizoprionodon sp. teeth have a slightly re-curved crown; cutting edges finely serrated or smooth, mesialedge curved, distal heel with a notable notch; roots straight, low,with a deep and transverse groove (Fig. 5.19). Rhizoprionodondiffers from Sphyrna by having a notch in distal heel and shortercrown. Rhizoprionodon sp. from the Gatun Formation measuresfrom CH¼2.5 and 3.3 mm and CW¼3.9 and 5.6 mm.

Material.—Six isolated teeth; indeterminate position: UF267978, UF 267980–267981, SMU 76461, SMU 76464 andSMU 76475.

Occurrence.—Lower Gatun localities 1, 15 (Figs. 1, 2).Remarks.—Cappetta (1987) stated that teeth from Rhizoprio-

nodon are less than CH¼4 mm. However, teeth from Pungo RiverFormation measured from CH¼3.2 to 5.2 mm and CW¼4.3 to 5.7mm (Purdy et al., 2001). Total length in extant adult individualsaverages in about TL¼1 m (Compagno, 1984). Extant specimensof this genus are mainly distributed in the Atlantic Ocean,


including Rhizoprionodon lalandii, Rhizoprionodon porosus, andRhizoprionodon terraenovae (Compagno, 1984). Extant R.lalandii occurs normally in lagoons and estuaries. R. porosus isfound usually close inshore. Rhizoprionodon terraenovae inhabitscoastal warm, temperate, and tropical waters, usually less than 10m in depth (Compagno, 1984; Compagno et al. 2005).

Family SPHYRNIDAE Gill, 1872Genus SPHYRNA Rafinesque, 1810

SPHYRNA LEWINI (Griffith and Smith, 1834)Figure 5.20

Description.—Shyrna lewini have a stout to slender crown,cutting edges either smooth or weakly serrated, thick and bulkyroot and a deep transverse groove. The S. lewini specimens fromthe Gatun Formation have a well-developed notch on the distaledges and the crowns are inclined (Fig. 5.20). Shyrna lewini isdifferentiated from other Sphyrna species by having smooth toweakly serrated cutting edges. The teeth measurements rangefrom CH¼2.7 and 5.4 mm and CW¼5.2 and 11.0 mm.

Material.—Four isolated teeth; uppers: SMU 76454, SMU76458 and SMU 76462; lower: SMU 76449.

Occurrence.—Lower Gatun locality 15 (Figs. 1, 2).Remarks.—This species is among the most abundant of the

hammerhead sharks. In the Neotropics, it has been reported fromthe Miocene of Cuba (Iturralde-Vinent et al., 1996; MacPhee etal., 2003). Extant individuals have a cosmopolitan distributionand occur in coastal warm-temperate and tropical seas, rangingfrom the surface to at least 275 m in depth (Compagno, 1984).

SPHYRNA MOKARRAN (Ruppell, 1837)Figure 5.21

Description.—Shyrna mokarran teeth exhibit triangular shape,increasingly oblique crown, serrated cutting edges, thick andbulky root, and deep transverse groove (Fig. 5.21). Shyrnamokarran differs from other species of Sphyrna by having oneheel more pronounced than the other. Teeth from the GatunFormation measure from CH¼7.6 to 9.4 mm and CW¼9.6 to 16.4mm.

Material.—Four isolated teeth; uppers: UF 237909–UF237912.

Occurrence.—Lower Gatun locality 1 (Figs. 1, 2).Remarks.—This species is not well documented in the fossil

record. In the circum-Caribbean region, it has only previouslybeen reported from the Miocene of Cuba, although there is nodescription of the specimens (MacPhee et al., 2003). Modern S.mokarran has a circumtropical distribution and inhabits coastal-pelagic and semi-oceanic, tropical habitats, from 1–80 m(Compagno et al., 2005).

SPHYRNA sp.Figure 5.22

Description.—Serrated and labio-lingually flattened crown;apex inclined or slanted distally; acute notch; thick, bulky root;transverse groove present (Fig. 5.22). The mesial cutting edge ofSphyrna sp. is generally convex and slightly sigmoid; cusps areslender. Sphyrna sp. teeth from the Gatun Formation have thickercrowns and weaker serrations than Sphyrna lewini. Themeasurements for this taxa range from CH¼3.1 to 8.9 mm andCW¼7.4 to 10.6 mm.

Material.—Thirty four (34) isolated teeth; upper: UF 242868;lower: UF 238020; indeterminate position: UF 242869–242870,UF 245862, UF 245865, UF 245922–245924, UF 245952–245958, UF 247265–247266, UF 247293, UF 266788–266790,SMU 76459, SMU 76463, SMU 76465, and SMU 76475.

Occurrence.—Lower Gatun localities 1, 15 (Figs. 1, 2).Remarks.—Cappetta (1987) established the maximum tooth

size for this genus to be CH¼20 mm, much larger than the teeth

studied here. This suggests that individuals from the GatunFormation were small. Extant species inhabit all temperate andtropical seas, and are found mostly in coastal waters (Compagno,1988).

Subdivision BATOIDEA Compagno, 1973Order RAJIFORMES Berg, 1940

Family RHYNCHOBATIDAE Garman, 1913Genus RHYNCHOBATUS Muller and Henle, 1837RHYNCHOBATUS LUEBBERTI (Ehrenbaum, 1914)

Figure 6.1, 6.2

Description.—In apical view, convex-shaped crown; angularmesial and distal sides; occlusal surface with fine granularornamentation above the smooth labial side; lingual edge smooth;shallow mesial and distal depressions with an irregularly-shapedand well-developed uvula (Fig. 6.1). In basal view, root relativelyhigh and situated on the lingual half of the base of the crown;labial part angled; lingual part with a well-developed trilobation.A large foramen is present in the median groove, as well as asmaller mesial and distal foramen (Fig. 6.2). This specimenmeasures 2.6 mm long and 3.2 mm wide.

Material.—One isolated male tooth; lower lateral: UF 247214.Occurrence.—Lower Gatun locality 1 (Figs. 1, 2).Remarks.—Rhynchobatus luebberti is a large batoid from the

eastern Atlantic, reaching up to TL¼3 m. It is a benthic speciesliving on soft mud or sand in the intertidal zone, up to 70 m depth;however, it is not generally found in waters deeper than 35 m(Compagno and Marshall, 2006). The dentition of R. luebberti hasbeen described and illustrated by Herman et al. (1997), where it ispossible to appreciate the variable ornamentation.

RHYNCHOBATUS sp.Figure 6.3, 6.4

Description.—In apical view, crown with arched transversekeel from mesial to distal sides dividing the labial and lingualparts. Labial part with a depression followed by second shorterkeel, a parallel irregular folding, and a convex smooth surfacecompleting the labial edge of the crown. Lingual part with smoothsurface, shallow mesial and distal depressions, and well-developed uvula (Fig. 6.3). In basal view, root relatively high,situated on the lingual half of the base of the crown; labial partangled; the lingual part with well-developed trilobation. Foramenpresent in medial groove (Fig. 6.4). This specimen measures 0.9mm long and 0.9 mm wide.

Material.—One isolated tooth; lateral: UF 271961.Occurrence.—Lower Gatun locality 1 (Fig. 1, 2).Remarks.—Symphysial teeth have been reported as quite wide,

up to about CW¼5 mm (Cappetta, 1987), in contrast to thespecimen collected from the Gatun Formation. In the Neotropics,it otherwise has been reported in the Miocene of Venezuela(Aguilera and Rodrigues de Aguilera, 2001). This genus consistsof six extant species found in the tropical and subtropical Indo-Pacific, with a single species in the eastern Atlantic: R. luebberti(Compagno and Marshall, 2006).

Order MYLIOBATIFORMES Compagno, 1973Family UROTRYGONIDAE McEachran et al., 1996

Genus UROBATIS Garman, 1913UROBATIS sp.

Figures 6.5, 6.6, 7.1, 7.2

Description.—In apical view, crown with a trapezoid contour;lingual half of the occlusal area with a transverse depressionedged by an irregular transverse crest, labial part slightly convexwith a coarse reticulated ornamentation with deep depressions(Fig. 6.5). Lingual side smooth, V-shaped, and with transversekeel with irregular ornamentation that runs from the mesial to the


distal sides of the crown; labial side with a decreasing contourthat fits on the next tooth. The crown-root junction lies in ashallow depression. In basal view, root asymmetric with two welldifferentiated lobes, the right lobe is much more slender than theleft lobe, indicating a lateral position; it is oblique toward the rearof the tooth, and slightly diverges at the root base; root base witha well-developed deep median groove that encloses a centralforamen (Fig. 6.6). Lingual and labial foramina and root coatingare absent. The flat crown is a diagnostic feature of a female. Thisspecimen is 0.5 mm long and 0.9 mm wide.

A partial caudal spine was also recovered. The enameloid ofthe dorsal section has serrations (Fig. 7.1) whereas the ventralside does not (Fig. 7.2). Dorsal spine groove present, ventral partconvex. This specimen is 21.0 mm long.

Material.—One isolated tooth, female, lateral: UF 267987. Onecaudal spine: UF 247226.

Occurrence.—Lower Gatun localities 1, 5 (Figs. 1, 2).Remarks.—Urotrygonidae (American round rays) were for-

merly included in the Urolophidae (Indo-Pacific round rays; seeMcEachran et al., 1996). This family of round rays inhabitsestuaries, lagoons, and neritic waters (usually in less than 15 m)of tropical and warm temperate seas (Allen and Robertson, 1994;Ebert, 2003). The tooth morphology of the Gatun specimen isvery similar to the extant ray Urobatis halleri. Fossil specimensare described in Cappetta (1987), with a maximum width of 2mm. Today, U. halleri is restricted to the eastern Pacific, fromCalifornia to Colombia, and is the most common species of thefamily (McEachran et al., 1996). Urobati halleri is commonlyfound in sand rubble or rock bottoms close to reefs, and is ademersal species occurring in depths of no more than 91 m(Michael, 1993; Allen and Robertson, 1994). With regards to thespine, Schwartz (2007) described the caudal spines of stingrays

FIGURE 6—Batoid micro-teeth from the late Miocene Gatun Formation, Panama. 1, 2, Rhynchobatus luebberti (Ehrenbaum, 1914), UF 247214, male tooth,lower lateral in apical and basal view, respectively; 3, 4 Rhynchobatus sp., UF 271961, lateral tooth in apical and basal view, respectively; 5, 6, Urobatis sp. UF267987, female tooth, lateral in apical and basal view, respectively; 7–10 Taeniura aff. grabata (Geoffroy Saint-Hilaire, 1817): 7, 8, UF 267992, female tooth,lateral in apical and basal view, respectively; 9, 10, UF 267994, male tooth, anterior in apical-labial and basal view, respectively; 11–14 Mobula munkiana(Notarbartolo Di Sciara, 1987): 11, 12, UF 267993, female tooth in apical and basal view, respectively; 13, 14, UF 267989, male tooth in apical and basal view,respectively; 15, 16, Mobula thurstoni (Lloyd, 1908), UF 267995, female tooth, indeterminate position in apical and basal view, respectively; 17–20, Mobulahypostoma (Bancroft, 1831): 17, 18, UF 267985, female tooth in labial-apical and basal view, respectively; 19, 20, UF 267988, male tooth in apical and basalview, respectively.


from the northwest Pacific Ocean, indicating that spinemorphology can be good indicators of their habitat. Themorphology of the Gatun specimen described here correspondsto a benthic environment.

Family DASYATIDAE Jordan, 1888Genus TAENIURA Muller and Henle, 1837

TAENIURA aff. GRABATA (Geoffroy Saint-Hilaire, 1817)Figure 6.7–6.10

1817 Taeniurops grabata GEOFFROY SAINT-HILAIRE, p. 218, pl.XXV, figs. 1, 2.

Description.—In apical view, female teeth with a broad crown,rounded transverse keel dividing the crown into lingual and labialpart; labial margin of the crown less arched than the lingualmargin; both margins join in the mesial and distal marginalangles; lingual central ridge absent; lingual surface slightlyconvex with ornamentation consisting on coarse irregular costulesalong the transverse keel. Labial surface with a deep depressionalong the transverse keel, and well-developed reticulatedornamentation in the labial margin (Fig. 6.7). In basal view,labial part of the crown with a broad and relatively flat rim thatgradually narrows to half its width. Crown-root junction situatedon a deep depression in the center of the basal surface of thecrown. Root narrow, moderately high, with a slightly oval tocircular shape; root base with a well-developed deep mediangrove that encloses two or three central foramina. Lingual andlabial foramina, and root coating are absent (Fig. 6.8). UF 267994shows male diagnostic character consisting of a pointed crownwith irregular reticulated ornamentation (Fig. 6.9, 6.10). Mea-surements of specimens range from 1.5 to 3.1 mm long and 1.9 to3.0 mm wide.

Material.—Five isolated teeth; female, anteriors: UF 267991and UF 267998; female laterals: UF 267992 and UF 267997;male, anterior: UF 267994.

Occurrence.—Lower Gatun localities 1, 5; middle Gatunlocality 3 (Figs. 1, 2).

Remarks.—Dental description and images have been published(Herman et al., 1998; p. 158, pls. 18, 19), but only representfemale dentition. Taeniura grabata is recorded in the easterncentral, the southeast Atlantic Ocean and in the western IndianOcean. It is a demersal species occurring in marine neritic tropicalor warm temperate waters from 10 to 300 m depth, on sand androck-sand bottoms (Serena et al., 2009).

Family MYLIOBATIDAE Bonaparte, 1838Genus AETOBATUS Blainville, 1816

AETOBATUS cf. NARINARI (Euphrasen, 1790)Figure 7.3, 7.4

Description.—Crown mesio-distally flatted, almost straight andarched outward; interlocking ornamentation almost absent, butexhibit relatively fine vertical costules on the lingual and labialsurfaces; a narrow lingual ledge is present. Root shifted inwardsfrom the crown, so that the labial side overhangs the labial rootedge interlocking the teeth. Root polyaulacorhizid (i.e., vascu-larized through many small foramina concentrated in severalgrooves running parallel from the labial to the lingual face) withnumerous evenly shaped basal grooves, each with scatteredforamina along the center of the groove (Fig. 7.3, 7.4). Lowerteeth mesio-distally V-shaped. Upper teeth almost straight. UF247202–UF 247205 specimens represent a single tooth measuring66.0 mm long, 8.0 mm wide and 4.5 mm high.

Material.—One complete tooth: UF 247202–247205; 21fragments of isolated teeth, uppers: UF 247201, UF 247228–247229, UF 247230–247232, UF 247236, UF 247241–247246;lowers: UF 247215 and UF 247229; indeterminate position: UF266761–266763, UF 266765, UF 266767, UF 266769, 271103–271104, and UF 271104.

Occurrence.—Lower Gatun localities 1, 5, 6, 7, 11 (Figs. 1, 2).Remarks.—This is a cosmopolitan species occurring in tropical

continental or insular platforms within the neritic zone. They areabundant in warm to temperate-warm shallow water deposits(Compagno and Last, 1999).

Genus MYLIOBATIS Cuvier, 1816MYLIOBATIS cf. CALIFORNICA (Gill, 1865)

Figure 7.5, 7.6

Description.—Low crown with smooth surface. Abrasionmarks on lateral side preserved; triangular contour. Interlockinggranular ornamentation on lingual and labial faces; narrow lingualledge present. Root shifted inward from the crown, so that thelabial crown edge overhangs the labial root edge interlocking theteeth. Teeth of M. californica differ from the genus Rhinoptera inhaving a much smaller ledge between the crown and the root. UF247209–UF 247210 are a pair of articulated incompletesymphysial teeth measuring 33.0 mm long, 13.0 mm wide and8.0 mm high. The occlusal face is eroded, evidencing these arefunctional teeth (Fig. 7.5, 7.6).

Material.—One articulated pair of incomplete teeth; upper: UF247209–UF 247210 and six fragments of isolated teeth;indeterminate position: UF 247211, UF 266760, UF 266764,UF 266766, UF 266768, and UF 271105.

Occurrence.—Lower Gatun localities 1, 5, 6 (Figs. 1, 2).Remarks.—Myliobatis californica occurs in the eastern Pacific,

from tropical to subtropical waters in the inner continental orinsular platform of the neritic zone. They are frequently found inbenthopelagic and demersal environments, and in both saltwaterand euryhaline habitats from Oregon to the Pacific coast ofMexico. In the Pacific, M. californica and Myliobatis peruvianusare very similar in morphology, but the latter is smaller, andrestricted to Ecuador, Peru and Chile. The geographic ranges ofboth species overlap in the Galapagos Islands (Michael, 1993).

FIGURE 7—Batoid macro-teeth from the late Miocene Gatun Formation,Panama. 1, 2, Urobatis sp.: 1, UF 247226, dorsal side, 2, UF 247226, ventralside; 3, 4, Aetobatus cf. narinari (Euphrasen, 1790), UF 247202–UF 247205,upper teeth in labial and lingual view, respectively; 5, 6 Myliobatis cf.californica (Gill, 1865), UF 247209–UF 247210, symphysial teeth in labialand lingual view, respectively; 7, 8 Rhinoptera cf. steindachneri (Evermannand Jenkins, 1892), UF 247240, upper symphysial tooth in labial and lingualview, respectively.


Genus RHINOPTERA Kuhl in Cuvier, 1829RHINOPTERA cf. STEINDACHNERI (Evermann and Jenkins, 1891)

Figure 7.7, 7.8

Description.—Upper teeth straight; crown enlarged and flatwith a hexagonal contour in the occlusal face. Lingual face with acentral depression between the crown and the root; labial facewith a transverse ledge, which interlocks with the next tooth inthe dental plate. Root shifted inwards from the crown on thelingual and the labial faces; crown overhangs the root edgeinterlocking the teeth. Root polyaulacorhizid with numerous lobesand grooves, not extending beyond margin of crown. Uppersymphysial teeth larger than laterals (Fig. 7.7, 7.8). In lower teeth,the lateral longitude is short, and the lingual and labial facesdistance is wider than in upper teeth. Teeth of Rhinoptera cf.steindachneri from the Gatun Formation are elongated and moresymmetrical and slender than Myliobatis. Complete specimensmeasure from 4.0 to 5.0 mm long, 3.0 to 26.0 mm wide, and 3.0 to5.0 mm high.

Material.—Thirty three (33) teeth; 10 complete and 23incomplete isolated teeth; uppers: UF 247216, UF 247219–247220, UF 247222, UF 247224–247225, UF 247235, UF247237–247238, UF 247240, UF 247244–247245, and UF247247; lowers: UF 247206–UF 247208, UF 247212–UF247213, UF 247217–247218, UF 247221, UF 247223, UF247227, UF 247233–247234, and UF 247239; indeterminateposition 266758–UF 266759, UF 266770, UF 271106–271107,UF 271110, and UF 271112.

Occurrence—Lower Gatun localities 1, 2, 5, 7 (Figs. 1, 2).Remarks.—Rhinoptera steindachneri is restricted to the eastern

Pacific where it is a benthopelagic species occurring exclusivelyin the neritic zone of the inner part of continental and insularplatforms (Smith and Bizzarro, 2006).

Genus MOBULA Rafinesque, 1810MOBULA MUNKIANA (Notarbartolo Di Sciara, 1987)

Figure 6.11–6.14

Description.—Teeth of M. munkiana from the Gatun Forma-tion presents both female and male morphology. Female teethdisplay an almost hexagonal crown and smooth enameloid;mesial edge with a wide triangular cusp followed by a smallerone and then a transversal edge crown; root short with respect tothe crown (Fig. 6.11–6.12). Male teeth have a wide triangularcrown and smooth enameloid with two wide triangular points,and two smaller lateral denticles, one on each side (mesial anddistal). Root slender, positioned at the very basal lingual edge ofthe crown, with two wide lobes elongated mesio-distally, andseparated by a wide groove with large foramina (Fig. 6.13,6.14). The labial basal edge overhangs the empty space of theabsence of the root for the interlocking system between theteeth. UF 267990 shows a wide and triangular main central cuspwith two wide triangles directed to the lingual side, and two lowlateral cusps; the mesial cusp is wider, whereas the distal cusp isslender. In the labial side, the basal edge of the crown showswide irregular folding and a root elongated mesial-distally. Theroot is positioned at the very lingual edge. UF 267999 displays amale tooth morphology, smooth enameloid; pointed crown withlateral prolongation directed to the lingual side of the mouth;basal crown almost oval in basal view. The specimens of theGatun Formation measure from 0.5–1.2 mm long and 0.9–2.3mm wide.

Material.—Four isolated teeth; female lowers: UF 267989–267990, female upper: UF 267993 male lower: UF 267999.

Occurrence.—Lower Gatun localities 1, 2, 5 (Figs. 1, 2).Remarks.—Teeth of the genus Mobula are generally small.

Mobula munkiana occurs in the eastern tropical Pacific. It is apelagic and demersal species, usually found in coastal shallowwater habitats of around 15 m depth (Bizzarro et al., 2006).

MOBULA THURSTONI (Lloyd, 1908)Figure 6.15, 6.16

Description.—Specimens from the Gatun have a female toothmorphology. UF 267995 has an almost oval shape at the base ofthe crown (Fig. 6.15). In basal view, apical edge of the crownwith four triangular cusps; the enameloid on the labial face showsirregular folding. Root oriented mesio–distally, much smallerthan the crown, and with two wide lobes (Fig. 6.16). This tooth is0.6 mm long and 1.1 mm wide. UF 267996 displays a crownmesio-distally elongated with five irregular points and enameloidon the labial crown with irregular folding. This tooth measures0.6 mm long and 2.0 mm wide.

Material.—Two isolated teeth, female, lowers: UF 267995–267996.

Occurrence.—Lower Gatun locality 1 (Figs. 1, 2).Remarks.—This species has a circumtropical distribution. It

occurs in the open ocean, neritic waters, sub-tidal aquatic beds,and coral reefs; in depths of between intertidal waters and 100 m(Clark et al., 2006).

MOBULA HYPOSTOMA (Bancroft, 1831)Figure 6.17–6.20

Description.—Teeth of M. hypostoma from the Gatun Forma-tion present both female and male morphology. Femalemorphology consists on an elongated crown with a 458 inclinationin direction to the lingual side, three isolated cusps, two laterals,one on each side (mesial and distal); smooth enameloid (Fig.6.17); and root much smaller than the crown with two lobes (Fig.6.18). Male morphology consists on a tripod crown; one widecentral main cusp, slender lateral cusps (Fig. 6.19); and root withtwo lobes separated by a nutritive groove (Fig. 6.20). UF 267986is an incomplete tooth consisting on a main wide cusp, and twoother cusps; root with two wide lobes separated by a widenutritive groove. Specimens from the Gatun Formation range insize from 0.5 to 0.6 mm long and 0.9 to 1.1 mm wide.

Material.—Three isolated teeth, female, lowers: UF 267985–267986; male, lower: UF 267988.

Occurrence.—Lower Gatun locality 5 (Figs. 1, 2).Remarks.—The extant M. hypostoma is a pelagic-neritic

species occurring in coastal tropical and subtropical waters ofthe western Atlantic (Bizzarro et al., 2009).

DIVERSITY AND TAXONOMIC COMPOSITION

Taking advantage of the ongoing excavations of differentoutcrops from the late Miocene Gatun Formation of Panama,here we review and describe all known material. Accordingly,we identified a total of 26 taxa belonging to five orders, ninefamilies, and 16 genera (Fig. 3) in 15 different localities (Figs.1, 2). Of this assemblage, only four species are now extinct (see† in Fig. 3); the remaining are extant and hence represent long-lived taxa. Most of the chondrichthyan species represented inthe Gatun Formation possess a fossil record at least from theMiocene, though some also occur in the Eocene and Oligocene.It has been proposed that the rate of evolutionary change insharks is much slower compared with other organisms (Martinet al., 1992). Based on tooth morphology of fossil and Recentspecimens, we can assert that the chondrichthyan fauna of thelate Miocene Gatun Formation has not changed significantly forseveral million years, and has been remarkably resilient tonumerous environmental changes, for example, and relevant tothis study, to the major geographic and oceanographic changesassociated with the closure of the CAS.

Gillette (1984) described 14 chondrichthyans from one singlelocality in the Gatun Formation. As stated earlier, we wereunable to resample that site due to loss of the relevant outcrops.


However, the material borrowed from SMU allowed us to makesome comparisons. While our identifications are fairly consis-tent with those of Gillette (1984), there are a number of keydifferences and additions that expand our knowledge ofchondrichthyan fauna of the Gatun Formation (Fig. 3).

The following species reported by Gillette (1984) are inagreement with our identifications: Ginglymostoma delfortriei,Carcharocles megalodon, Hemipristis serra, Carcharhinus sp.,and Physogaleus contortus. While no other teeth of G.delfortriei were collected during the present study, the SMUspecimens confirm the presence of this species in the GatunFormation. The fact that no further material was recoveredduring this study is not surprising given that these teeth aresmall and not typically found during typical surface collecting.However, we did not find this species during our screenwashingefforts either. Additional C. megalodon specimens werecollected during this study. The cosmopolitan nature of thespecies is documented by the presence of C. megalodon teethworldwide (Cappetta, 1987; Purdy, 1996; Purdy et al., 2001).The most common teeth found in the Gatun Formation areundifferentiated Carcharhinus, representing about 40% of thetotal sampled fauna (Fig. 3). This genus varies greatly in sizeand morphology (Naylor and Marcus, 1994), making it difficultto identify to the species level. The second most common taxonis H. serra, representing 15% of the total sampled fauna (Fig. 3).The presence of Physogaleus (Galeocerdo) contortus reportedby Gillette (1984) was confirmed by the collection of twospecimens in this study. It should be noted however, that thespecimens described in Gillette’s work were not present in theSMU collection for comparison.

There are a number of key differences and additions to thechondrichthyan fauna of the Gatun Formation resulting fromthis study. Gillette (1984) identified one white shark tooth(Carcharodon carcharias), describing it as being highly worn,missing its edges and serrations. However, this specimen wasalso missing from the SMU collection and we were thereforeunable to confirm the identification. Regardless, the presence ofa white shark tooth in the late Miocene is unlikely becausemodern C. carcharias does not become common in the fossilrecord until the Pliocene (Ehret et al., 2009, 2012). Withoutbeing able to study the specimen, it is difficult to speculatewhich species was represented by this fragmentary tooth. Theoriginal description lacks enough detail to be definitive, andtherefore the specimen could also be attributed to a small C.megalodon or perhaps the extinct mako shark Carcharodonhastalis (see Ehret et al., 2012 for discussion on the systematicof this species). However, no mako sharks have been recoveredfrom the Gatun Formation of Panama. The absence of this taxonmay be due to the typically bathyal or mesopelagic depth rangeof this species (Aguilera and Rodrigues de Aguilera, 2001).

Additional omissions in our study relative to Gillette’s (1984)original descriptions include Physogaleus (Galeocerdo) adun-cus, Sphyrna arambourgi, Sphyrna zygaena, and Isistius sp.These differences reflect the reanalysis and redescription of theoriginal material. The teeth from the SMU collection were notcatalogued until this study, making the identification of theindividual specimens described by Gillette (1984) somewhatproblematic. The teeth that Gillette (1984) referred as Phys-ogaleus (Galeocerdo) aduncus were missing from the SMUcollection and not available for comparison. Sphyrna arambour-gi and S. zygeana have been reidentified as the scallopedhammerhead shark (Sphyrna lewini) in this study. Themorphology of these fossil teeth is more consistent with S.lewini than either S. arambourgi or S. zygaena. Furthermore, thepresence of Isistius sp. in the Gatun Formation is refuted. Based

on its morphology, we interpret that the specimens Gillette(1984) referred to Isistius sp. belong to the sharpnose shark,Rhizoprionodon. In addition, five new specimens of Rhizoprio-

nodon were collected in this study. While lower Isistius teeth arepresent in the Miocene of Venezuela (Aguilera and Rodriguesde Aguilera, 2001) and in the Pliocene of North Carolina (Purdyet al., 2001), no upper teeth have been described from the fossilrecord, which may be related to their weaker mineralization(Cappetta, 1987). The reidentification of these teeth toRhizoprionodon is also more consistent with the habitatreconstruction of the Gatun Formation. This species inhabitswarm coastal waters, whereas Isistius tends to be an oceanic,epipelagic to bathypelagic shark (Compagno, 1984; Purdy et al.,2001). Therefore, on the basis of paleoecological evidence ofother sharks and associated invertebrate taxa, its presence in theGatun Formation would be highly irregular. An additional 21taxa have been identified from the Gatun Formation of Panama(see þ in Fig. 3). Gillette (1984) reported the presence ofAetobatus sp. and Myliobatis sp.; however these specimens weremissing from the SMU collection, and we were therefore unableto confirm the identification. Nevertheless, it is possible that ourrecords of Aetobatus aff. narinari and Myliobatis cf. californica

are the same species that Gillette had reported.

PALEOBIOGEOGRAPHY

The modern-day pattern of separate Pacific and Atlanticfaunas was derived from a large, once contiguous Eocene–Miocene province (Woodring, 1966, 1974) that encompassedthe tropical Eastern Pacific and the Caribbean. Gillette (1984),in comparing the fauna of the Gatun Formation to that ofEcuador, Florida, and North Carolina, recognized many of thefeatures of Woodring’s (1966, 1974) proposed Tertiary Carib-bean faunal province and extended it further to the north, toinclude the southeast Atlantic coast of North America. Studiesof benthic foraminifera (Collins et al., 1996) from the GatunFormation show a strong Caribbean affinity. This is explainedby an effective biogeographic restriction between Pacific andCaribbean surface waters (Collins et al., 1996; Kirby et al.,2008) by the time the Gatun sediments deposited. Concurrently,most of the chondrichthyan taxa from the Gatun Formation havealso been reported in other Miocene Caribbean marineassemblages of the Neotropics (see Systematic Paleontologysection and Fig. 8).

On the other hand, most of the taxa described here haverelated modern species that have a cosmopolitan distribution intoday’s oceans, except for Carcharhinus perezi, which isrestricted to the Caribbean Sea (Fig. 8). The genus Rhizoprio-nodon has extant representatives mainly distributed in theAtlantic Ocean (Rhizoprionodon terranovae, Rhizoprionodon

lalandii, and Rhizoprionodon porosus, Compagno, 1984). Of thebatoids, Rhynchobatus luebberti and Mobula hypostoma arecurrently restricted to the Atlantic Ocean; Taeniura aff grabata

is distributed in both the eastern Atlantic and the Indian Oceans;and Myliobatis cf. californica, Rhinoptera cf. steindachneri andMobula munkiana are currently restricted to the eastern Pacific(Fig. 8).

Regardless of the strong Caribbean affinity of the fossils fromthe Gatun Formation, the chondrichthyan fauna has modernmixed biogeographic affinities, including cosmopolitan andPacific distributions. This suggests that around 10 million yrago, a connection between the two oceans was likely maintainedand that despite the ongoing shoaling of isthmus region (Monteset al., 2012b), the chondrichthyan fauna was not isolated inCentral America.


PALEOENVIRONMENT AND PALEOECOLOGY

Previous studies of the Gatun Formation indicate that this areawas a shallow-water embayment with depths between 20 and 40m and salinity conditions similar to those found in large bays(Coates and Obando, 1996; Teranes et al., 1996, 1999; Hendy,2013). Based on depth preferences of extant chondrichthyans

related to the fossil taxa occurring in the Gatun Formation, weassert that this area was a shallow paleoenvironment. Many ofthe chondrichthyans that inhabited this environment occurred inthe neritic zone, above 200 m depth (Fig. 8, dashed line). Taxawith larger depth ranges (greater than 200 m) represent a smallproportion of the total assemblage (3.14% of total of specimens)and include Carcharhinus falciformis (three specimens, 0.38%),Carcharhinus obscurus (six specimens, 0.75%), Carcharhinus

plumbeus (five specimens, 0.63%), Sphyrna lewini (six speci-mens, 0.75%) and Taeniura aff. grabata (five specimens,0.63%; Fig. 2). In addition, the absence of other pelagic fauna

commonly found in Miocene assemblages of the region such asAlopias, Carcharodon, Isurus and Odontaspis (Portell et al.,2008; Aguilera and Rodrigues de Aguilera, 2001; Ward andBonavia, 2001; Iturralde-Vinent et al., 1996; Laurito, 1999),supports the hypothesis that the Gatun Formation represents ashallow-water environment.

While Hendy (2013; Fig. 8) indicated considerable fine-scalefluctuations in paleobathymetry through the stratigraphy of theGatun Formation, those variations are beyond the resolution ofthe depth preference analysis carried out here. Nevertheless,they might be used as a framework for interpreting changes inchondrichthyan taxonomic composition (Fig. 9). For the mostpart, taxonomic composition changes little throughout thestratigraphy, but it is noteworthy that no batoids have beenrecorded from the deepest water section (upper member) of theGatun Formation. The absence of batoids in this section is notsurprising, given their preferences for shallow continentalwaters (Carpenter and Niem, 1999).

Tooth-size comparisons of specimens from the GatunFormation were made when possible with measurements ofchondrichthyan specimens from two formations exposed at theLee Creek Mine, Aurora, North Carolina (Purdy et al., 2001):the Pungo River Formation (middle Miocene) and the YorktownFormation (early Pliocene). These formations are older andyounger, respectively, than the late Miocene Gatun Formation(11.8 to 8.4 million yr ago; Coates, 1999). Based on the size ofthe isolated teeth found within the Gatun Formation, we assertthat chondrichthyans inhabiting Panama during the late Miocenewere generally smaller than those at the comparable sites.Nevertheless, we cannot conclude that the small size observed in

FIGURE 8—Biogeography and depth preferences of the chondrichthyans from the Gatun Formation. Key: e¼extant distribution; x¼fossil occurrences in theNeotropics; dashed line separates the neritic zone (below the 200 m); gray box indicates total depth range observed by Hendy (2013) from the Gatun Formation.References for the bathymetry of each taxa are presented in the Systematic Paleontology section.


the Gatun Formation is related to juvenile stages of the differenttaxa without a careful study of the ontogenetic changes thatoccur in each species, nor without estimates of their total length.

On the other hand, rigorous analyses have been made for thespecies Carcharocles megalodon in Pimiento et al. (2010).Based on different size comparisons and estimates of their totallength, the relatively small size of C. megalodon teeth from theGatun Formation indicates a preponderance of juveniles, andsuggests that this species used northern Panama as a paleo-nursery area. Nursery areas are geographically discrete zonesthat can be shared by multiple species, and where neonates arepresent and juveniles are found in high proportions (Castro,1993; Heupel et al., 2007; Pimiento et al., 2010).

In this study, we were able to collect further 22 C. megalodonspecimens beyond those that were included in the 2010 work.Twelve teeth were complete enough to estimate the total length

(TL) of the individuals following the methods described inPimiento et al. (2010). Our estimates show that most of the newindividuals were also juveniles, including one neonate present inour new subsample (Table 1). These results are in agreementwith the nursery area hypothesis proposed for C. megalodon.Additionally, our observation of a generally small tooth-size inthe chondrichthyan fauna, suggests that other species may havehad high proportions of juveniles, and that different sharkspecies could have shared this nursery. More analyses on theother chondrichthyan taxa from the Gatun Formation are neededin order to test this hypothesis.

CONCLUSIONS

We have analyzed the diversity, taxonomic composition,biogeography, paleoenvironments and paleoecology of thechondrichthyans from the late Miocene of Panama based on

FIGURE 9—Stratigraphy, chondrichthyan taxonomic composition, and paleobathymetry of the Gatun Formation. The abundance of the eight most abundanttaxa (.20 elements) is pooled for each 50 m intervals of the composite stratigraphy in Figure 2. Each gray box representing estimated paleobathymetry indicatesthe shallowest and deepest estimated paleodepth for each 50 m interval (adapted from Hendy, 2013).


historical and new collections. Given the extensive excavationsthat have taken place in the recent years at the classic and newlocalities of the Gatun Formation, and the possibility that theseoutcrops will not exist in the future, this effort provides a uniqueopportunity to study this ancient fauna. The well-sampled GatunFormation has a diverse chondrichthyan fauna composed by 26long-lived taxa with mixed biogeographic affinities. While ouridentifications were fairly consistent with previous studies,additional collecting and taxonomic revisions resulted in agreatly enlarged and thoroughly revised faunal list. This studyallows us to better understand an ancient chondrichthyan faunaand confirms previous observations of paleobathymetry andhabitat use for this area during the late Miocene.

ACKNOWLEDGMENTS

This project was funded by NSF EAR 0418042, PIRE 0966884,Autoridad del Canal de Panama contrato SAA-199520-KRP,Ricardo Perez S.A., M. Tupper, National Geographic Channel,and the Smithsonian Institution. We thank the Direccion deRecursos Minerales of Panama for collecting permits; R. Hulbert,J. Bloch, G. Morgan for beneficial suggestions; G. Hubbell and R.Leder for helping with the identification of the material; A.Rincon, F. Rodriguez, C. De Gracia, and the Panama CanalProject Field Team in the Center for Tropical Paleobiology andArchaeology at STRI for helping with the collection; D. Winklerof SMU and M. Florence of the USNM for access to collections;and M. Shippritt, R. G. Reina, and C. Symister for logistical

support. Lastly, we thank J. Ceballos for editing an earlier versionof this manuscript, and O. Aguilera and an anonymous reviewerwho helped improving it. C. Jaramillo thanks the University ofYale Edward P. Bass Distinguished Visiting EnvironmentalScholarship and A. Hendy acknowledges support from the JonA. and Beverly L. Thompson Endowment. C. Pimiento thanks J.McLaughlin for support. This is University of Florida Contribu-tion to Paleontology number 628.

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TABLE 1—Carcharocles megalodon teeth measurements from the GatunFormation, Panama (modified from Pimiento et al., 2010). Neonates: T¼upto 4 m; juveniles: T¼4–10 m; adults: TL¼from 10 m (Gottfried et al., 1996).

Specimen CW (mm) CH (mm) Position TL (m)

UF 237898 53.0 50.0 upper anterior 5.9UF 237914 31.4 46.4 upper lateral 8.0UF 237949 35.7 32.9 upper anterior 3.9UF 237950 47.7 54.2 lower anterior 7.3UF 237951 26.8 17.6 upper lateral 3.1UF 237952 43.2 31.3 upper lateral 5.4UF 237953 30.9 24.5 lower lateral 7.2UF 237954 41.7 41.2 upper anterior 4.9UF 237955 28.4 28.5 upper anterior 3.4UF 237956 44.9 28.1 lower anterior 16.8UF 237957 26.7 19.4 upper posterior 13.8UF 237959 16.1 16.0 lower anterior 2.2UF 242801 31.2 27.5 lateral 6.4UF 242802 45.1 41.0 upper lateral 7.1UF 242803 40.8 34.7 upper lateral 6.0AT04-17-1 43.2 43.8 lower anterior 6.2AT04-41-2 60.3 56.4 upper anterior 6.7AT06-9-1 57.7 60.1 upper anterior 7.1UF 245844 20.6 11.2 lower posterior 10.0UF 245852 73.2 70.9 upper lateral 10.8UF 245885 39.6 36.6 upper lateral 5.2UF 245886 45.6 40.5 upper lateral 7.0UF 245996 31.8 25.9 lower lateral 13.1UF 245995 62.2 63.2 lower anterior 11.0UF 246002 35.0 24.5 upper posterior 11.5UF 246003 52.4 45.4 upper lateral 6.4UF 245925 23.2 19.2 upper posterior 13.7CTPA 6671 74.7 72.3 upper anterior 8.6UF 242804þ 29.4 34.7 lateral 6.9UF 247248þ 72.3 61.8 upper anterior 8.6UF 246846þ 24.3 28.2 upper lateral 3.5UF 266953þ 12.1 22.5 posterior 9.6UF 247250þ 37.3 40.7 anterior 4.8UF 247251þ 42.5 45.1 lower anterior 6.0UF 247252þ 44.9 48.2 upper lateral 7.8UF 247254þ 50.4 63.4 upper lateral 8.7UF 257576þ 47.9 43.9 lower anterior 6.7UF 257577þ 35.8 39.7 upper lateral 17.0UF 257578þ 50.1 51.1 upper anterior 5.9UF 257579þ 37.6 41.2 upper lateral 17.9

þ New subsample of specimens collected during this study.


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SHARKS AND RAYS (CHONDRICHTHYES ......SHARKS AND RAYS (CHONDRICHTHYES, ELASMOBRANCHII) FROM THE LATE MIOCENE GATUN FORMATION OF PANAMA CATALINA PIMIENTO,1,2,3 GERARDO GONZA´LEZ-BARBA,4