Michelle Spaulding

The Theropod Furcula

The furcula is a structure formed by the midline fusion of the clavicles. This is the element which is unique to theropods and is important for understanding the link between birds and other theropods. New specimens from basal theropods suggest that the furcula appeared very early in theropod history. We review furcula development, function, and morphology, as well as the anatomical terminology applied to it. Furcular morphology is highly variable in crown‐group avians but is rather conserved among nonavian theropods. Here we review, or describe for the first time, the furculae in many nonavian theropods. Furculae occur in nearly all major clades of theropods, as shown by new theropod specimens from the Early Cretaceous of China and a close inspection of previously collected specimens. Informative phylogenetic characters pertaining to the furcula occur throughout Theropoda, though care should betake to consider taphonomic effects when describing furcular morphology. J. Morphol., 2009.

Phylogeny of the Carnivoramorpha: The impact of postcranial characters

Previous analyses of the mammalian clade Carnivoramorpha have tended to sample only cranial and dental character systems, particularly those that included early Cenozoic taxa, Viverravidae and basal Carnivoraformes (the latter being a paraphyletic array of taxa traditionally referred to as the ‘Miacidae’). In this study we add more than 100 postcranial characters to an existing dataset dominated by cranio-dental characters. The addition of the new characters permits the inclusion of a large number of basal carnivoraforms, known solely or predominantly from postcranial characters, that previously would have been ‘unplaceable’ in a phylogenetic analysis. The resultant phylogeny recovers most of the same clades identified in previous studies, but resolves some relationships differently within the basal carnivoraforms. A novel (unnamed) monophyletic subclade of the Carnivoraformes is recovered, supported in part by characters from both the prior and new datasets. The inclusion of a substantial suite of postcranial characters expands the ability to assess the relationships of basal carnivoramorphan taxa, and permits the inclusion of many taxa represented only by incomplete material.

ANATOMY OF THE POSTCRANIAL SKELETON OF "MIACIS" UINTENSIS (MAMMALIA: CARNIVORAMORPHA)

ABSTRACT This paper provides the first detailed description of the only known postcranial skeletal elements of “Miacis” uintensis. The morphology of the skeleton differs markedly from previously described “miacids” (a paraphyletic assemblage of early fossil carnivoramorphans), invalidating the notion that all “miacids” were very similar in their postcranial morphology and locomotor styles. The majority of the differences indicate an animal less well adapted to an arboreal lifestyle than has been inferred for other early “miacid” carnivoramorphans. A phylogenetic analysis clearly nests “Miacis” uintensis within the paraphyletic array of taxa previously referred to as the “Miacidae,” in a position closer to the crown clade Carnivora than is Vulpavus, a “miacid” whose postcranium has been previously described. When compared with the early canid Hesperocyon, this specimen shares many features thought to relate to the acquisition of a more terrestrial mode of life. This result indicates that, in contrast to prior models suggesting arboreality for all “miacids,” at least one independent ‘descent from the trees’ occurred much earlier within the array of stem carnivoramorphan taxa.

Response to comment on "The placental mammal ancestor and the post-K-Pg radiation of placentals".

Tree-building with diverse data maximizes explanatory power. Application of molecular clock models to ancient speciation events risks a bias against detection of fast radiations subsequent to the Cretaceous-Paleogene (K-Pg) event. Contrary to Springer et al., post–K-Pg placental diversification does not require “virus-like” substitution rates. Even constraining clade ages to their model, the explosive model best explains placental evolution.

On the Cranial Osteology of the African Palm Civet, Nandinia binotata (Gray, 1830) (Mammalia, Carnivora, Feliformia)

ABSTRACT The external and endocranial surfaces of the skull of the African palm civet, Nandinia binotata (Gray, 1830), are described and illustrated in detail based on 30 specimens (from Carnegie Museum of Natural History and American Museum of Natural History). With the inclusion of a newborn and six juveniles with deciduous dentitions, a reasonable ontogenetic series is represented. The bone-by-bone descriptions are primarily based on the condition in an adult female and the newborn with consideration of variation across the sample. The principal cranial foramina are treated in a glossary, and the hyoid apparatus and larynx are described from a single specimen. The sample exhibits a remarkable degree of variability in cranial features that are often used as different states of characters in phylogenetic analysis (e.g., number and position of palatal foramina, the orbital mosaic, and composition of the lacrimal foramen). Nandinia binotata, the only taxon in the Nandiniidae, has been identified as the most basal extant feliform in recent phylogenetic analyses of both molecular and morphological data. It has long been recognized that its ear region with its uninflated auditory bulla exhibits a primitive level of organization. To assess the primitive nature of the skull of N. binotata, comparisons are made with three extant carnivorans, the felid Felis catus Linnaeus, 1758, the viverrid Genetta genetta (Linnaeus, 1758), and the canid Canis lupus Linnaeus, 1758. Of the three, N. binotata shares numerous resemblances across the skull with G. genetta, which accounts for its historical inclusion in the Viverridae. Whereas aspects of the ear region of N. binotata are clearly unique among extant carnivorans, the rest of its skull is not similarly so.

A Reexamination of the Carnivora Malleus (Mammalia, Placentalia)

Authoritative anatomical references depict domestic dogs and cats as having a malleus with a short rostral (anterior) process that is connected via a ligament to the ectotympanic of the auditory bulla. Similar mallei have been reported for representatives of each of the 15 extant families of Carnivora, the placental order containing dogs and cats. This morphology is in contrast to a malleus with a long rostral process anchored to the ectotympanic that is considered to be primitive for mammals. Our reexamination of extant carnivorans found representatives from 12 families that possess an elongate rostral process anchored to the ectotympanic. Consequently, the malleus also is a component of the bulla. In a subset of our carnivoran sample, we confirmed that the elongate rostral process on the ectotympanic is continuous with the rest of the malleus through a thin osseous lamina. This morphology is reconstructed as primitive for Carnivora. Prior inaccurate descriptions of the taxa in our sample having mallei continuous with the bulla were based on damaged mallei. In addition to coupling to the ectotympanic, the rostral process of the malleus was found to have a hook-like process that fits in a facet on the skull base in representatives from seven families (felids, nandiniids, viverrids, canids, ursids, procyonids, and mustelids); its occurrence in the remaining families could not be ascertained. This feature is named herein the mallear hook and is likewise reconstructed to be primitive for Carnivora. We also investigated mallei in one additional placental order reported to have mallei not connected to the ectotympanic, Pholidota (pangolins), the extant sister group of Carnivora. We found pholidotans to also have anchored mallei with long rostral processes, but lacking mallear hooks. In light of our results, other mammals previously reported to have short rostral processes should be reexamined.

Mammalian Petrosal from the Upper Jurassic Morrison Formation of Fruita, Colorado

ABSTRACT A partial petrosal from the Upper Jurassic Morrison Formation of the Fruita Paleontological Area of western Colorado preserving the pars cochlearis and part of the pars canalicularis is described. The endocast of the inner ear showing the cochlea, vestibule, lateral semicircular canal, and the terminal ends of the anterior and posterior semicircular canals is reconstructed from µCT scans. This specimen is only the fourth petrosal known from the Morrison Formation. Mammals known from Fruita include Fruitafossor windsheffeli Luo and Wible, 2005, the triconodontid Priacodon fruitaensis Rasmussen and Callison, 1981, the plagiaulacoid multituberculate Glirodon grandis Engelmann and Callison, 1999, and unnamed spalacotheriids and dryolestoids. The partial petrosal and its endocast share significant features with dryolestoids from the Upper Jurassic of Guimarota, Portugal, including a separate fenestra cochleae and cochlear canaliculus, and a cochlea that is coiled more than 200°. In light of these similarities, the Fruita petrosal is assigned to Dryolestoidea.