e-Journal Earth ScienceIindia, Vol. I (II), 2008, pp. 66-71 http://www.earthscienceindia.info/

Brissid echinoid Eupatagus L. Agassiz, 1847 from

The Khuiala Formation, Jaisalmer district,

Rajasthan, India

D. K. Srivastava1 and Hukam Singh2

1Centre of Advanced Study in Geology, University of Lucknow, Lucknow – 226 007,

India 2 Birbal Sahni Institute of Palaeobotany, Lucknow – 226 007, India

Email:sirdkdr@gmail.com

Abstract

The spatangoid genus Eupatagus L. Agassiz, 1847 is recorded, for

the first time, from the sediments of the Khuiala Formation (Early Eocene)

exposed near Habur, Jaisalmer district, Rajasthan, India. The specimens

are placed in a new species characterised by its large, oval test with mild

frontal sinus; convex aboral surface; flat oral surface; anteriorly eccentric

ethmolytic apical system; anteriorly eccentric kidney- shaped peristome;

long, petaloid ambulacral petals; longitudinally oval periproct at the

posterior truncation and imperforate, non crenulated tubercles.

Introduction

The paper records, for the first time, a brissid echinoid Eupatagus L. Agassiz, 1847

(Fischer,1966 and Smith, 2008) from the sediments of the Khuiala Formation (Early Eocene)

exposed at about 625 m west of Habur, Jaisalmer district, Rajasthan, India (Fig.1) as

Eupatagus rajasthanensis n. sp. The field work was carried out by the second author (HS)

jointly with Dr. J. S. Guleria, Birbal Sahni Institute of Palaeobotany, Lucknow, while the

palaeontological work has been carried out by the first author (DKS). Earlier, the three

echinoid genera recorded from Rajasthan (Sahni, 1955; Sahni and Bhatnagar, 1958;

Srivastava and Mathur, 1996 and Srivastava et al., 2008) are Recrosalenia (R.

jaisalmerensis from the Jurassic sediments), Echinocyamus (E. jaisalmerensis from the

Middle Eocene sediments) and Megapneustes (M. jaisalmerensis from the Early Eocene).

However, the genus Eupatagus L. Agassiz, 1847 has so far been reported in India from the

Tertiary rocks of Kachchh (Duncan and Sladen, 1883; Srivastava, 1981; Srivastava, 2004)

and Assam (Spengler, 1923) only.

Geology of the area

The isolated outcrops of the fossiliferous Mesozoic and the Cenozoic formations in the

Jaisalmer Basin are interspersed in the southeastern part of the basin within the desert

sands (Singh, 2006). The Tertiary sequence in the Jaisalmer Basin (Das Gupta, 1974;

Pareek, 1984; Singh, 1996; Singh, 2003; Sinha et al., 1998; Bhandari, 1999 and Singh,

2007) is represented by the Sanu, Khuiala, Bandha and Shumar formations in ascending

order. The stratigraphic succession of the studied area is given in Table-1.

Brissid echinoid Eupatagus L. Agassiz, 1847 from the Khuiala Formation, Jaisalmer district, Rajasthan,

India: D. K. Srivastava and Hukam Singh

Fig.1: Geological map of the area showing the fossil locality (after Singh, 2007)

Table- 1: Stratigraphic succession of the Palaeogene sediments in Jaisalmer area,

Rajasthan, India

Age Formation Member

(Surface)

Member

(Subsurface)

Pleistocene to

Sub-Recent

Shumar

Middle Eocene Bandah Bakhri Tibba

Batrewala

Limestone

Bakhri Tibba

Batrewala Limestone

Early Eocene Khuiala Khinsar

Tetakkar

Limestone

Upper Khinsar

Sirhera

Lower Khinsar

Tetakkar Limestone

Palaeocene Sanu

Mohammaed Dhani

Kharatar

Mohammaed Dhani

Cretaceous Abur/Pariwar

The age of echinoid-bearing horizon of the Khuiala Formation (calcareous sandy

marl) is constrained by the presence of index larger foraminifer Assilina lacunata Cizancourt

(Srivastava et al., 2008) which indicates an Early Eocene (Ypresian) age. The ostracode,

bivalve and other biotic elements previously described from the Khuiala Formation (Khosla,

1972; Das Gupta, 1974; Pareek, 1984; Ghosh, 1987; Bhandari, 1995; Singh, 1996; Singh,

1997 and Singh, 2003) are also consistent with this age assignment.

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Systematic Palaeontology

(Fischer, 1966)

Order: Spatangoida Clauss, 1876

Family: Brissidae Gray, 1855

Genus: Eupatagus L. Agassiz,

1847

Subgenus: Eupatagus L. Agassiz,

1847

Eupatagus (Eupatagus) rajasthanensis sp.

nov.

(Figure 2. a-g)

Material: 20 specimens, few broken and incomplete but preservation is fairly good;

(Holotype: 7097/BSIP/39528; Paratypes: 7097/BSIP/39529 to 7097/BSIP/39547).

Derivation of name: The species has been named after Rajasthan State (area of its

occurrence), India.

Diagnosis: The species is characterized by its large, oval test with mild frontal sinus;

convex aboral surface; flat oral surface; anteriorly eccentric ethmolytic apical system;

anteriorly eccentric kidney-shaped peristome; long, petaloid ambulacral petals;

longitudinally oval periproct at the posterior truncation and imperforate, non crenulated

tubercles.

Description: The specimens are characterized by a large, oval test with mild frontal

sinus, convex aboral surface, flat oral surface, highest point of the test at the centre of the

test, margin tumid and well rounded. The test is longer than wide and wider than high,

truncated towards posterior side and moderately keeled. Apical system anteriorly eccentric,

ethmolytic with four small and circular genital pores, the two anterior genital pores are

closer than the posterior ones. Paired ambulacra petaloid and flush with the test. Petal III

indistinct, petals I & V longer than the petals II & IV. Poriferous zones slightly depressed

and consists of inner circular and oval to slit like outer pores which are conjugated by a

deep groove. Periproct longitudinally oval, lies on the vertical posterior truncation and not

visible from the aboral side. Peristome on oral surface, anteriorly eccentric and kidney-

shaped. The peripetalous fasciole passes around the petals and do not indent in the

interambulacral areas. The subanal fasciole, however, is not visible. The test is ornamented

with imperforate, non-crenulated tubercles which are sunken in small scrobicules. These are

large, scarce and circumscribed by the peripetalous fasciole on the aboral side while orally

these are dense and small.

Dimensions (in mm):

Specimen No. Length

(L)

Breadth

(B)

Height

(H)

Ratio between L, B

& H

7097/BSIP 39528 (Holotype) 17.82 15.42 09.15 1.0 0.86 0.51

7097/BSIP 39529 (Paratype) 20.64 17.73 09.52 1.0 0.85 0.41

Brissid echinoid Eupatagus L. Agassiz, 1847 from the Khuiala Formation, Jaisalmer district, Rajasthan,

India: D. K. Srivastava and Hukam Singh

Fig. 2: a-g Eupatagus (Eupatagus) rajasthanensis n. sp. (Scale bars = 5.0 mm otherwise

as stated)

a. Aboral view [7097/BSIP 39528 (Holotype)]; b. Apical disc (bar = 1.0 mm)

[7097/BSIP 39530 (Paratype)]; c. Line drawing showing peripetalous fasciole; d.

Aboral view showing ambulacral plates in petals IV & V [7097/BSIP 39529

(Paratype)]; e. Oral view showing plates around peristome [7097/BSIP

39531(Paratype)]; f. Posterior view showing periproct [7097/BSIP 39532

(Paratype)]; g. Lateral view [7097/BSIP 39528 (Holotype)]

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Remarks: The new species is close to E. alatus Arnold and Clark described from the

Eocene sediments of Jamaica (Arnold and Clark, 1927) but it differs in having longer petals I

& V, posteriorly protruded test and lesser number of tubercles. It also differs from

Eupatagus cf. antillarum (Cotteau) reported from the mid-middle to low-late Eocene

sediments of Clarimont Formation, White Limestone Group, Jamaica (Donovan and Rowe,

2000) in having less broad oval test which is broadest in the middle and more anteriorly

eccentric apical system. Eupatagus (Eupatagus) rajasthanensis n. sp. differs from

Eupatagus (Eupatagus) rostratus (d’Archiac) reported from the Eocene and Oligocene

(Srivastava, 2004) and Oligocene and Miocene rocks of Kachchh (Duncan & Sladen, 1883)

in not having flexuous petals II & IV. It also differs from Eupatagus (Eupatagus) singhi

Srivastava described from the Middle Oligocene sediments of Kachchh (Srivastava, 1981) in

having moderate frontal sinus.

Type locality: About 625 m west of Habur, Jaisalmer district, Rajasthan, India.

Type horizon: Khuiala Formation (early Eocene).

Repository

All described, undescribed and photographed specimens of fossil echinoids

(Holotype: 7097/BSIP/39528; Paratypes: 7097/BSIP/39529 to 7097/BSIP/39547) have

been deposited in the Museum, Birbal Sahni Institute of Palaeobotany, Lucknow, India.

Acknowledgements: The authors express a deep sense of gratitude to Prof. A. K. Jauhri, Head,

Centre of Advanced Study in Geology, University of Lucknow, Lucknow and to Dr. N. C. Mehrotra,

Director, Birbal Sahni Institute of Palaeobotany, Lucknow for providing facilities and encouragement.

Dr. A. B. Smith (Natural History Museum, London) is thanked for critically reading through the original

manuscript and offering helpful comments. They are obliged to Prof. Ashok Sahni, Panjab University,

Chandigarh for suggestions. The financial assistance granted to the first author (DKS) by the

Department of Science and Technology, New Delhi for the laboratory work is thankfully acknowledged.

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