CRANIAL ANATOMY OF KRYPTOBAATAR DASHZEVEGI (MAMMALIA, MULTITUBERCULATA), AND ITS BEARING ON THE EVOLUTION OF MAMMALIAN CHARACTERS

By J. Wible, G. Rougier. 2000

100 citations recorded by the source corpus.

Abstract The cranial anatomy of the Mongolian Late Cretaceous multituberculate Kryptobaatar dashzevegi is described based on exquisitely preserved specimens collected from Ukhaa Tolgod and Tugrugeen Shireh in the Gobi Desert by joint expeditions of the American Museum of Natural History and the Mongolian Academy of Sciences. Most sutural relationships are preserved, enabling a bone-by-bone description of the skull and lower jaws exclusive of the nasal fossa and paranasal sinuses. A reconstruction of the principal components of the cranial nervous, arterial, and venous systems is facilitated by specimens with exposed endocranial surfaces. Comparisons with previously described multituberculates, other Mesozoic mammaliaforms, and extant mammals allow an assessment of major topics in the evolutionary morphology of the multituberculate and mammaliaform skull, as well as identification of Kryptobaatar as an appropriate model regarding most aspects of the multituberculate skull for future phylogenetic studies. Elements previously unknown or poorly known in multituberculates are described. Included are a complete jugal on the internal surface of the zygoma; the orbital mosaic and foramina, including the optic foramen, the metoptic foramen, the transverse canal, and the foramen for the pituito-orbital vein; and the endocranium with an extensively ossified primary braincase wall formed by the pilae metoptica and antotica. The latter pila is very robust compared with its ossified remnants in non-mammalian cynodonts and monotremes, suggesting that it is a derived multituberculate condition. The co-occurrence of the pilae metoptica and antotica in multituberculates is thus far unique among mammaliaforms, but agrees with the morphology expected to be primitive for Mammalia. This in turn implies an independent loss of an ossified pila metoptica in monotremes, marsupials, and Vincelestes or the loss of the pila metoptica in the ancestry of multituberculates and therians combined with the independent reacquisition of a neomorphic pila metoptica in multituberculates and eutherians. The absence of several elements from the multituberculate skull, controversial in nature, is confirmed, including the prenasal process of the premaxilla, the septomaxilla, the ectopterygoid, and the orbital process of the palatine. Also confirmed is the presence of several controversial elements in the multituberculate skull, including an alisphenoid with a reduced contribution to the braincase and an anterior lamina expanded dorsal to the alisphenoid. Competing anatomical hypotheses for several elements are addressed, including the function of the lateral pterygopalatine trough as muscle attachment and not for the auditory tube, the homology of the postorbital process on the parietal with that on the frontal, the identity of foramina in the anterior lamina as for mandibular nerve branches and not for the mandibular and maxillary nerves, and the function of the jugular fossa as primarily having housed a diverticulum of the cavum tympani and not large cranial nerve ganglia. The cranial arterial system in Kryptobaatar generally resembled that restored for other multituberculates and for other mammaliaforms, in particular the prototribosphenidan Vincelestes. Both Kryptobaatar and Vincelestes had a transpromontorial internal carotid artery, a stapedial artery that ran through a bicrurate stapes, ramus inferior, ramus superior, and an arteria diploëtica magna. The cranial venous system in Kryptobaatar resembled that described for other Mongolian Late Cretaceous multituberculates and for monotremes with the major exits of the dural sinuses having been the prootic canal and the foramen magnum. A revised diagnosis of Kryptobaatar distinguishes it from other djadochtatherians (the grouping that includes 10 of the 11 genera of Mongolian Late Cretaceous multituberculates) by a pterygoid canal either confluent with or barely separated from the carotid canal and a separate hypoglossal foramen.

Subfields: Nature and Landscape Conservation, Paleontology

View Paper: https://www.semanticscholar.org/paper/031c2703c653c61bab3b3779380415126e9e0e9f

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In Nature and Landscape Conservation

1. M. Novacek
2. J. Wible
3. M. Mckenna
4. G. Rougier
5. C. Muizon
6. Zhe‐Xi Luo
7. N. Giannini
8. D. Ksepka

In Paleontology

1. J. Wible
2. M. Novacek
3. R. Asher
4. Guillaume Billet
5. G. Rougier
6. C. Argot
7. F. Goussard
8. Sandrine Ladevèze

Citations in the corpus

• Alcidedorbignya inopinata, a basal pantodont (Placentalia, Mammalia) from the early Palaeocene of Bolivia: anatomy, phylogeny and palaeobiology (2015, background): “Posterior to these foramina, at the level of the anterior edge of the protocone of M2, is a pair of small accessory palatine foramina (see Wible & Rougier 2000: 77 for a review of the palatine foramina in mammals).”
• Relationships of Endemic African Mammals and Their Fossil Relatives Based on Morphological and Molecular Evidence (2003, background): “6, 8), Wible and Rougier (2000), and Asher (1999, 2001), we regard this structure as a foramen in the frontal bone connecting an intracranial sinus of the anterior braincase with the orbit and typically serving as a conduit for venous drainage and ethmoidal arteries and nerves.”
• In quest for a phylogeny of Mesozoic mammals (2002, background): “This is a derived feature shared by the monotremes Tachyglossus and Obdurodon (Musser and Archer 1998), although not Ornithorhynchus, by many (but not all) multituberculates (Kielan−Jaworowska and Hurum 1997; Wible and Rougier 2000), and by most trechnotherians (Krebs 1991; Rougier 1993; Hu et al.”
• NEW DATA ON THE SKULL AND DENTITION IN THE MONGOLIAN LATE CRETACEOUS EUTHERIAN MAMMAL ZALAMBDALESTES (2004, background): “…among extant forms, being found in dipodoid rodents (Bugge, 1971; Wible, 1984) and some chiropterans (Kallen, 1977; Wible and Davis, 2000), but has also been reconstructed for Asioryctes (Kielan-Jaworwoska, 1981), Vincelestes (Rougier et al., 1992), and multituberculates (Wible and Rougier, 2000).”
• Earliest Eutherian Ear Region: A Petrosal Referred to Prokennalestes from the Early Cretaceous of Mongolia (2001, methodology): “Among extant mammals, such companion veins are known for the platypus (fig. 4A; Wible and Hopson, 1995; Wible and Rougier, 2000), but are thought to be generally lacking in therians preserving the ramus superior and ramus inferior.”
• On the Cranial Osteology of Chiroptera. I. Pteropus (Megachiroptera: Pteropodidae) (2006, background): “…insectivorans (Novacek, 1986), the Paleocene metatherian Pucadelphys (Marshall and Muizon, 1995), the Late Cretaceous multituberculate Kryptobaatar (Wible and Rougier, 2000), the Late Cretaceous eutherian Zalambdalestes (Wible et al., 2004), the extant short-tailed opossum Monodelphis (Wible,…”