Lagomorpha, Macroscelidea, RODENTIA

Mammalogy

EEOB 625

13 February 2004

Order Lagomoprpha

• Are lagomorphs closely related to Rodentia? - similar cranial morphology & adaptive zones

- no consensus from molecular studies (Vaughan)

• Lagomorphs arose in Asia (Paleocene) underwent radiation in N. America in Oligocene - Miocene

• Comparisons with Rodentia: - incisors & adaptations to herbivory I: 2/1 vs. I: 1/1

- Jointed skull with diastema & fenestrated maxillary - cursorial adaptations: long hind legs (in Leporidae)

Order Lagomorpha – 80 species

• Worldwide distribution except Australia

• Family Leporidae: 11 genera, 54 species

Competitive herbivores with derived cursorial adaptations in diverse habitats around the World

• Family Ochotonidae: 2 genera, 26 species Smaller with sorter hind limbs and ears Nearctic and Paleactic in mountainous habitats

Unusual nutritional strategy of “hay making”

Order Macroscelidea: Elephant Shrews

• Family Macroscelididae: 4 genera, 15 species

Medium-sized, 50-500 g, in the Ethiopian since the Miocene

• Related to insectivores or elephants?

• Reduction of digits to 4 in pes, & 3 (?) in pes

• Wide variety of habitats, feed on a variety of invertebrates, mostly termites & ants

Rodentia: the gnawing victors

• About 43% of all mammals are rodents• Criteria of success of a taxon __, ___, ___• Why are rodents so successful? (Exam II)

How do we approach such a question?• Origin and Evolution: Fossils from the late

Paleocene in Asia and North America

- Paramys, a squirrel‑like ancestral genus from the Paleocene

Therapsid

Multituberculate

Paramys sp

Feldhamer (1999)

Rodentia: the gnawing victors

• How do we classify 2004 species, 443 genera, and 29 extant families?

• Derived characters (Vaughan Table 18-1)

• Parallel evolution obscures relationships and make classification to suborder difficult

• A classification based on the infraorbital foramen, masseter, & zygomatic arch (Vaughan 18-2)

• Sciuromorpha, Myomorpha, Hystricomorpha

Paramys spCobert (1969)

Zygo-masseteric Patterns in Rodents

• Sciuromorphous – Primitive, squirrel-like masseter lateralis originates on rostrum and zygomatic plate, infraorbital foramen, small

• Myomorphous – Derived, mouse-like medial masseter originates on rostrum (maxillary)

& passes through a slightly enlarged infraorbital foramen.

• Hystricomorphous – Highly derived, porcupine-like. Medial masseter originates on rostrum and passes through a greatly enlarged infraorbital Typical of several Neotropical families

Medial masseter & the infraorbital foramen of a myomorph rodent

Rodent Dentition & Mastication

• Is mastication the key to rodents’ success?• Incisors: enamel on labial surface only and

rootless for continuous growth

• Diastema ‑ a common gap in herbivores • Molars & premolars similar in appearance but

different in development.

• Marvelous masticatory movements of the mandible: the elongated glenoid fossa and the moveable mandibular symphysis

Heteromyidae

Seeds & beads

View from below glass of a foraging kangaroo rat

The EndLagomorpha,

Macroscelidea, RODENTIA I

Family Dipodidae

• Jerboas & jumping mice (51 species)

• Nearctic, Palearctic, Ethiopian,

Dipodidae (= Zapodidae)

Zapus or Napaeozapus ?