Lagomorpha, Macroscelidea, RODENTIA Mammalogy EEOB 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, 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: F ossils 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 sp Cobert (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? I ncisors: 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 End Lagomorpha, Macroscelidea, RODENTIA I

Family Dipodidae Jerboas & jumping mice (51 species) Nearctic, Palearctic, Ethiopian,

Dipodidae (= Zapodidae) Zapus or Napaeozapus ?