Der Bau der Canini bei den Paulchoffatiidae (Multituberculata; Ober-Jura)

Canines are preserved among Multituberculata only in the upper jaw of the Paulchoffatiidae, the Pinheirodontidae and the North American genusGliodon Engelmann &; Callison, 1999. They resemble the anterior premolars (p^1–3) in the morphology of their crown, but they differ from them by the presence of only one root. In the present paper, 126 isolated canines of the Paulchoffatiidae from the Guimarota coal-pit in Portugal are treated. They show a wide morphological variation, from bicuspid to pentacuspid expression, and they can be grouped into 18 morphological units (Tab. 1). The bicuspid canines (11 specimens) show one buccal and one lingual cusp, arranged side by side, the latter normally being larger than the former. In the tricuspid canines (32 specimens) the cusps (one buccal and two lingual) are arranged in a triangle, with a great variation in the position of the cusps to each other. Tetracuspid canines (69 specimens) are the dominating group. Two buccal and two lingual cusps are present, which differ markedly in their largeness and their position to each other. The teeth differ also much in the shape of their crown. The pentacuspid canines (14 specimens) show two buccal and three lingual cusps. The variation in the arrangement of the cusps and in the shape of the crown is similar as in the tetracuspid specimens. One or two small cuspules can be present at the anterior border of the crown additionally to the main cusps in the canines. Tricuspid and tetracuspid canines are present also in the skulls of the Paulchoffatiidae, whereas bicuspid and pentacuspid canines are known only as isolated specimens. In the Pinheirodontidae the canines are tricuspid or tetracuspid, inGlirodon they are unicuspid. The Paulchoffatiidae and Pinheirodontidae — Paulchoffatiid line sensuKielan-Jaworowska &; Hurum, 2001 — are characterized by increasing premolarization of the upper canines. With that they differ markedly from all other multituberculates where the canini become reduced.     

The Inner Ear of Two Late Cretaceous Multituberculate Mammals, and Its Implications for Multituberculate Hearing

The inner ear of the Late Cretaceous multituberculates Nemegtbaatar gobiensis and Chulsan-baatar vulgaris is described from serial sections and enlarged models. The size and proportions of the inner ear as a whole are as expected for extant small mammals. The lengths of the cochlea (Nemegtbaatar gobiensis, 3.0 mm, Chulsanbaatar vulgaris, 2.0 mm) are comparable to those of other multituberculates, when ratios of length of the cochlea to skull length are calculated. The vestibule is not as expanded in the two taxa as in Lambdopsalis, ?Meniscoessus, and ?Catopsalis; the estimated volume for Nemegtbaatar gobiensis is 9 mm³. A slightly laterally curved, anteriomedially directed cochlea, relatively robust ear ossicles, and the estimations of the area of the tympanic membrane and stapedial footplate in Chulsanbaatar suggest high-frequency hearing but a relatively low sensitivity to low-decibel sounds. The semicircular canals of Nemegtbaatar and Chulsanbaatar are fully developed; the size of the anterior, posterior, and lateral canals and their angles and proportions are comparable to those of extant mammals of similar size. The anterior semicircular canal of Nemegtbaatar forms a smooth half-circle and thus is more derived than the angular canal of Ornithorhynchus. The notable differences between the ratio of the width of the lateral semicircular canal to skull length and the size of the vestibule in Nemegtbaatar and the Paleocene multituberculate Lambdopsalis bulla are probably related to different modes of life.     

Absence of ptilodontoidean multituberculates from Asia and its palaeogeographic implications

Gobibaatar parvus Kielan-Jaworowska 1970, formerly the only representative of the Ptilodontoidea in Asia, is recognized to be a junior synonym of Kryptobaatar dashzevegi Kielan-Jaworowska 1970 and allocated to the Taeniolabidoidea. Members of the Ptilodontoidea are thus currently unknown in Asian faunas. Chulsanbaataridae Kielan-Jaworowska 1974 is a junior synonym of the Eucosmodontidae Jepsen 1940. The absence of Ptilodontoidea in Asia gives further support to the theory of one-way Late Cretaceous dispersal of mammals from Asia to North America. The Marsupialia and Ptilodontoidea originated in the New World and never reached Asia, whereas the Taeniolabidoidea and Eutheria originated in Asia and dispersed to North America during the Late Cretaceous.     

An X-radiographic and SEM study of the osseous inner ear of multituberculates and monotremes (Mammalia): implications for mammalian phylogeny and evolution of hearing

Multituberculate petrosals with well-preserved, three-dimensional internal anatomy from the Late Cretaceous/early Paleocene Bug Creek Anthills, Montana, U.S.A., are described from X-radiographic and SEM images, as well as from conventional visual observations, and are compared with the anatomy of the osseous inner ear in monotremes and in primitive non-therian and therian mammals. Results of this study indicate that: (1) the cochlea of at least some multituberculates retained a lagena, previously known only in monotremes among mammals; (2) an enlarged vestibule evolved in several lineages of multituberculates independently, and hence is not a synapomorphy of the order; (3) the cochlear canal lacks osseous laminae in support of the short, wide basilar membrane, which was probably inefficient in responding to high-frequency airborne vibrations; and (4) consequently, bone-conducted hearing in some multituberculate species may have been important in interpretation of their surroundings. Comparisons with the inner ear of monotremes and primitive therians indicate that curvature of the cochlea and cribriform plates for passage of vestibulocochlear nerve branches through the petrosal are unlikely homologues between monotremes and therians. From non-therian to therian mammals, there is a distinct morphological gap in the inner ear transition, characterized by acquisition of a number of neomorphs in the therian inner ear; an intermediate stage has yet to be discovered.     

Mammalian tooth marks on the bones of dinosaurs and other Late Cretaceous vertebrates

Abstract: We describe bones from the Late Cretaceous of Alberta – including bones of large dinosaurs, a femur from the aquatic reptile Champsosaurus, and a dentary from the marsupial Eodelphis– that bear tooth marks made by animals with opposing pairs of teeth. Of the animals known from the Late Cretaceous of North America, only mammals are capable of making such tooth marks. In particular, multituberculates, which have paired upper and lower incisors, are the most likely candidates for the makers of these traces. The traces described here represent the oldest known mammalian tooth marks. Although it is possible that some of these tooth marks represent feeding traces, the tooth marks often penetrate deep into the dense cortices of the bone. This raises the possibility that, much as extant mammals gnaw bone and antler, some Cretaceous mammals may have consumed the bones of dinosaurs and other vertebrates as a source of minerals. However, none of the tooth marks described here resemble the extensive gnaw traces produced by Cenozoic multituberculates or rodents. This suggests that specialized gnawing forms may have been rare or absent in the Late Cretaceous of North America.     

Evolutionary analysis of the middle and inner ear of Late Jurassic multituberculates

We describe three previously unreported specimens of petrosal bones of paulchoffatiid multituberculate mammals, collected from strata of Late Jurassic age in the Guimarota lignite mine of Leiria, west-central Portugal. The new fossils allow correction, supplementation, and confirmation of anatomical details, thus refining knowledge of general adaptation in the ear region among Jurassic multituberculates. Virtually all observed characters in the paulchoffatiid otic region are primitive relative to homologous features seen among Late Cretaceous and younger representatives of the Multituberculata; we recognize few unique otic specializations in paulchoffatiids that would preclude ancestry to later multituberculates. The plesiomorphic nature of paulchoffatiid ear regions provides no evidence in support of the hypothesis of a special, sister-group relationship between multituberculates and Late Cretaceous/Cenozoic marsupials plus placentals. Used in isolation, objective evidence derived from paulchoffatiid ear regions is consistent with interpretation of multituberculate divergence from other mammals predating the stem to living monotremes and postdating the stem to extinct morganucodontids. More broadly based comparative studies among Mesozoic mammals, however, suggest that independent acquisition of similarly advanced mammalian features was a pervasive theme among evolutionary histories of early mammals, probably including multituberculates. Although the phylogenetic position of multituberculates relative to other mammalian groups has yet to be unequivocally resolved, we suggest that a very early divergence of the group remains a distinct possibility.     

FOSSORIAL ADAPTATIONS OF A TAENIOLABIDOID MULTITUBERCULATE MAMMAL FROM THE EOCENE OF CHINA

<正> Fragments of the postcranial skeleton of s taeniolabidoid multituberculate,? Lambdopsalis bulla, from the Eocene of Chins are described. These consist of cervical vertebrae C2-C3 (fused), a fragment of the neural arch of C4, and complete C5-C7, thoracic vertebrae T1-T3, and two humeri, which are the first Complete multituberculate humeri ever described. The fusion of C2 and C3, and the stout structure of the humerus with a very large deltopectoral crest, a wide distal end, and prominent radial and ulnar condyles, indicate a fossorial mode of life for? L. bulla. These postcranial elements and a wide flattened, skull with a vertical occipital plate, suggest adaptstions seen in some modern golden moles and cricetid rodents such as Myospalax that dig with claws and displace the soil with the head.     

Phylogeny and Systematics of Multituberculate Mammals

We present a synopsis of high-rank multituberculate systematicsand a manually generated cladogram illustrating multituberculate interrelationships. We divide the Multituberculata into the paraphyletic suborder 'Plagiaulacida', an apparently monophyletic suborder Cimolodonta, and one family incertae sedis. Within 'Plagiaulacida' we recognise three informal lines: paulchoffatiid (three families), plagiaulacid (three families) and allodontid (two families and the genus Glirodon). The Cimolodonta are divided into an informal Paracimexomys group; three superfamilies: Ptilodontoidea, Djadochtatherioidea (new), and Taeniolabidoidea (restricted to Taeniolabididae); and five families (superfamily incertae sedis): Eucosmodontidae, Microcosmodontidae, Cimolodontidae, Boffiidae, and Kogaionidae; and some genera incertae sedis. New characters used in our analysis are (1) a tendency of molar cusps to coalesce; and (2) ornamentation of grooves, pits, and ridges on the molars. We argue that the Ptilodontoidea, and less certainly also the Cimolodontidae and Boffiidae, might have originated from amongthe plagiaulacid line, a possible intermediate link being the Paracimexomys group. The remaining Cimolodonta might have originated from unknown members of the Paracimexomys group with separated molar cusps and smooth enamel. The origin of two types of prismatic enamel and a relationship between them are stumbling blocks in understanding the origin of the Cimolodonta; we conclude that microprismatic enamel made its appearance only once. Revised diagnoses of high-rank multituberculate taxa, including lists of all known genera, are given.     

First Record of Stygimys (Mammalia, Multituberculata, Eucosmodontidae) from the Paleocene (Puercan) Part of the North Horn Formation, Utah, and a Review of the Genus

A single tooth referred to Stygimys kuszmauli recovered at the Gas Tank Hill locality from Puercan strata of the North Horn Formation represents the first record of Stygimys from Utah. S. kuszmauli now occurs in both proposed north–south late Puercan biogeographic provinces, which reduces statistical support for provinciality. A new species from Texas, Stygimys vastus, is described. Of the five species previously referred to Stygimys, S. kuszmauli, Stygimys camptorhiza, Stygimys jepseni, and Stygimys teilhardi are valid, but Stygimys cupressus is synonymous with S. kuszmauli. The type of S. jepseni is restricted to a single p4 as the m1 thought to be from the same individual represents another multituberculate genus. Five sites, including Gas Tank Hill that comprise the Gas Tank Hill Local Fauna are widely dispersed in slumped strata which may differ in age, are located in a mostly floodplain depositional setting, and are small surface collected samples. Therefore, biogeographic analyses that compare the Gas Tank Hill Local Fauna to large samples collected from channel fills using screenwash techniques should be employed with caution. Stygimys has a relatively broad geographic and geochronologic distribution, but it is usually rare in Late Cretaceous and Early Paleocene mammalian assemblages. The recent recovery of Stygimys after more than 60 years of collecting in the North Horn Formation suggests that further sampling in other non-marine basins in Western North America will eventually yield additional specimens of the genus.