Vertebrate

Recent fossil discoveries of early cetaceans and sirenians document the functional transitions that occurred as each group adapted to a completely aquatic existence, but the timing and path of their ecological transition remain uncertain. We analyzed the stable-isotope composition of tooth enamel from several early members of each group to reconstruct the dietary, foraging, and habitat preferences of basal taxa. Carbon isotope (␦ 13 C) values provided evidence of foraging within freshwater, terrestrial, and marine environments, including seagrass beds, whereas oxygen isotope (␦ 18 O) variation was used as a measure of commitment to aquatic habitats. Enamel samples were collected from four regions (south Asia, north and west Africa, and southern Europe) spanning the late early Eocene (ca. 53.5 Ma) to the late Eocene (ca. 36 Ma). Sirenian and cetacean taxa included species that were likely capable of some terrestrial locomotion, and more specialized forms that were morphologically fully aquatic. Cetacean ␦ 13 C and ␦ 18 O values indicate that some early members of this group (some pakicetids) inhabited freshwater environments, but later members (e.g., remingtonocetids, protocetids, and basilosaurids) moved quickly into estuarine and marine environments. Low ␦ 18 O variation confirms that all of these early forms were primarily aquatic, but ␦ 13 C and ␦ 18 O values for early sirenians indicate an early transition to a marine seagrass diet without any evidence of an intermediate connection to freshwater habitats.

An articulated partial skeleton, including a nearly complete skull and left forelimb, of a crocodylomorph reptile from the Upper Triassic Chinle Formation of Ghost Ranch, New Mexico, is referable to Hesperosuchus agilis Colbert, 1952. It contributes much new information on the skeletal structure of this previously poorly known taxon. A large, circular palpebral bone is present in each orbit. The quadratojugal is particularly well preserved and suggests a reinterpretation of this element in related taxa including Sphenosuchus. Previous analyses of sphenosuchian relationships reached conflicting results, and a critical review of the characters used in these analyses is presented. A phylogenetic analysis of basal crocodylomorph taxa provides weak support for sphenosuchian monophyly, placing Hesperosuchus with Saltoposuchus, Dibothrosuchus, and Sphenosuchus.

OBJECTIVE: In the chordate and vertebrate central nervous system, sensory and motor nerve tracts cross from one side to the other as they connect the brain with sensory receptors and motor neurons. These "decussations," crossings in the form of an X, relate each side of the brain to the opposite side of the body. The protochordates derive from an invertebrate ancestor, but no such contralateral arrangement occurs in any invertebrate phylum. No adaptive benefit of decussation has been established. What might explain the evolution of decussation?

METHOD: A brief review of relevant features of comparative morphology of invertebrates, chordates and vertebrates leads to an explanatory model of decussation.

RESULT: A "somatic twist model" of invertebrate-vertebrate transition accounts for decussations as byproducts of a more momentous change; the relocation of the neuraxis from the ventral to the dorsal aspect of the body. Evidence is presented that this inversion proceeded by means of a twisting of the body 180 degrees on its axis just behind its anterior pole. This rotation aligned the neuraxis with the dorsal head ganglia and brain and by twisting the nerve tracts it brought decussation in its wake.

CONCLUSION: Decussation evolved as a byproduct of a genetically determined partial inversion of the body plan, which resulted in a 180 degree rotation posterior to the brain and oropharynx.

In this article, hypotheses about the origin, evolution and dispersal of Megantereon are reviewed using the fossil specimens included in previous comparative studies as well as the remains identified in the late Pliocene site of Fonelas (Spain) and the early Pleistocene localities of Lantian, Lingyi, Longdan, Renzidong (China), and Untermassfeld (Germany). The validity of the two species proposed by , Megantereon cultridens and M. whitei, is evaluated using tooth measurements and multivariate statistical methods. The hypothesis of sexual dimorphism as an explanation for the morphological variability of Megantereon is tested with a large sample of sexed individuals of Panthera pardus and Panthera leo. Results obtained indicate similar or even smaller differences in tooth dimensions between M. cultridens and M. whitei than between sexes in both leopards and lions, except in the case of the lower fourth premolar. However, in spite of a substantial overlap between both Megantereon species in the size of the upper canine, this tooth reverses the differences found for other tooth measurements, because M. cultridens shows larger cheek teeth on average than M. whitei but smaller sabers. This is confirmed by principal components and discriminant analyses, which reveal that sexual dimorphism in leopards and lions is a matter of tooth size and not of relative proportions and argues against the interpretation of M. cultridens and M. whitei as the sexes (males and females, respectively) of a single species. These results indicate that M. cultridens and M. whitei are valid species, because the differences in tooth measurements exceed those expected from sexual dimorphism and do not reveal the effects of biased sampling. Finally, an analysis of jaw anatomy reveals biomechanical differences between both Megantereon species, related to the relative efficiency of the biting muscles at the level of the lower carnassial.

A new locality named EI Pel illal (Cerro del Pueblo Formation, Late Cretaceous, Campanian) in the southeastern area of the State of Coahuila, Mexico yields an assemblage of vertebrates that is important for correlation due to its frequent occurrence in other localities along the Cerro del Pueblo Formation outcrops. It is located in the Municipio de Ramos Arizpe, Coahuila. Among the vertebrates found are: fishes (Lepisosteidae; Amiidae [cf. Melvius sp.]); turtles (Trionychidae, Chelydridae [cf. Protoehelydra sp.], Kinosternoidea [cf. Hoplo- ehelys sp.], an undetermined kinosternoid genus, and ?Pleurosternidae [Compsemys vieta]) ; Crocodilians Neosu- chia (Goniopholididae) ; and Eu suchia and a pterosaur (Pterodactyloidea). Dinosaurs found incl ude a hadrosaurine hadrosaur, a new Troodontidae, and other indeterminate theropods. The El Pelillal Locality is interpreted as a fre shwater environment possibly influenced by tides. The fauna of the EI Pelillal loca lity, Cerro del Puebl o Formation, resembles southern U.S . Campanian-Maastrichtian faunas but lack s the prevalence of baenid, adocid, Basilemys and Nanhsuingchelyd turtles.

The Terlingua local fauna is a rich assemblage of predominantly terrestrial micro vertebrates from the Upper Cretaceous Aguja Formation of Trans-Pecos Texas. Marine invertebrates (which include elements of both Cretaceous Western Interior and Gulf Coast zoogeographic provinces) from conformably underlying strata suggest that the fauna is of late Campanian age, probably correlative with Judithian assemblages of the Western Interior. A Judithian “age” for the fauna is further supported by its mammal and theropod assemblages, and by the faunas of overlying deposits. The previously reported diversity of the Aguja Formation, which we summarize, is significantly enriched by this new fauna. The fauna also fills a major gap in the biogeography of Campanian terrestrial vertebrates.Notable occurrences in the Terlingua local fauna include the therian mammal Gallolestes, previously known only from Baja California, and a hitherto unrecorded type of primitive ‘tribothere.’ At least 4 marsupial and 6 multituberculate taxa are present, several of which represent new taxa. Squamates comprise at least 10 taxa, including xenosaurs, necrosaurs, glyptosaurines, scincids, teiids, and a snake, several of which represent new taxa. In addition, the fauna includes at least 7 dinosaurs, 1 pterosaur, 2 crocodylomorphs, 3 turtles, 3 lissamphibians, 3 actinopterygians, and 8 chondrichthyans. Wood, amber, leaves, seeds, pollen, molluscs, and dinoflagellates are also preserved. The fauna is not strictly comparable to others from the Western Interior. It includes taxa that are either endemic or otherwise known only from relatively low latitudes, indicating an appreciable degree of latitudinal differentiation among Campanian terrestrial faunas bordering the Western Interior seaway.

The discovery of the smallest Triceratops skull (UCMP 154452) provides a new ontogenetic end member for the earliest stage of ceratopsid (Centrosaurinae plus Chasmosaurinae) cranial development. The lack of co-ossification among the parietal, squamosals, postorbitals, quadratojugal arch, and the braincase preserves sutural contacts and bone surfaces that later become obscured in adults. The ability to document the early development and morphology of the horns and frill in Triceratops allows a reevaluation of their functional roles. UCMP 154452 shows that the cranial ornamentation of the frill and the postorbital horns were not restricted to adults, but began at an early age in this species. This evidence supports the hypothesis that the function of ceratopsid horns and frills was potentially important for visual communication and species recognition because in this young form it could not have functioned in sexual display. Although some features of UCMP 154452 anticipate or mimic the adult character states, some braincase characters recapitulate the juvenile and adult stages of more basal neoceratopsians.

Six new occurrences of carnivorous mammals from Wadi Moghra, early Miocene, Egypt, are described, and the implications of these taxa for interpreting the biogeography of early Miocene mammals are discussed. The new taxa include two hyaenodontid creodonts (Buhakia moghraensis, gen. et sp. nov., and cf. Teratodon) and four carnivorans: an amphicyonid (Cynelos, sp. nov.), two viverrids s. l. (Herpestides aegypticus, sp. nov., and Ketketictis solida, gen. et sp. nov.), and a stenoplesictid (Moghradictis nedjema, gen. et sp. nov.). Previously only two carnivorous mammals, both large creodonts (Hyainailouros fourtaui, Megistotherium osteothlastes), had been reported from Moghra. Together, the eight carnivorous taxa now known from Moghra include not only some representatives of widespread genera common to localities across Eurasia and Africa, but also a number of unique faunal elements, including three new genera and five new species. Evidence for two alternate hypotheses concerning the timing of carnivore migrations events are discussed: 1) an early Miocene (ca. MN 3) event followed by a slightly later (MN 4-5) one; or 2) an even earlier first migration in the late Oligocene-early Miocene (MN 1 or even MP 30), considered here to be the more likely scenario.

The aigialosaur Carsosaurus marchesetti is represented by a nearly complete skeleton from the Upper Cretaceous (Cenomanian-Turonian) of Slovenia. Dermal girdle elements include portions of the clavicles and a small interclavicle with a short anterior process. Endochondral girdle elements include a small scapula and large unfenestrated coracoid. A mineralized sternum is also present. The carpus is anguid-like and consists of ten ossified elements. Reduction of the procoelous nature of centrum articular surfaces is restricted to the caudal series. The type of C. marchesetti is the largest aigialosaur specimen known (> 1.5 m) and has proportionally larger propodials than any other aigialosaur. Phylogenetic reconstruction places Carsosaurus within a polytomous clade composed of all known aigialosaurs. Aigialosaurs are the sister-group to Mosasauridae, forming the Mosasauroidea, and are within Anguimorpha but distinct from Varanoidea. Supposed synapomorphies of varanids and mosasauroids are identified as either plesiomorphies ofAnguimorpha, or as misidentified homologs. Results of a principal component analysis of limb measurements suggest that aigialosaurs occupy a position on a functional continuum reflective of terrestrial not aquatic animals. Morphometric criteria cannot validate the exclusion of Carsosaurus from the Aigialosauridae.

An analysis of 80 thin-sections of the long bones of a relatively large and presumably adult specimen of Confuciusornis sanctus, a basal bird from the Early Cretaceous of China, reveals osteohistological patterns similar in some ways to those of extant birds of approximate size, but different in other ways. The fibrolamellar tissue typical of its cortex is commonly laid down by adult birds at standard estimates of 10 m or more radial growth per day. If this rate were characteristic of its ontogeny, Confuciusornis could have reached maturity in 20 weeks or less. These tissue patterns, read straight, suggest lower growth rates than in the larger immediate relatives of Confuciusornis, the coelurosaurian dinosaurs, as well as in large extant birds, taxa that reached their large adult size relatively quickly. However, tissues of the inner cortex, as well as new analyses of rates in living variants of the fibro-lamellar tissue complex, suggest far faster growth and an estimated time to maturation as short as 8-13 weeks, longer than in most small living birds but commensurate with larger birds or relatively slowly growing birds such as tinami.

A new species of tilapiine cichlid, Oreochromis lorenzoi, is described from the late Miocene (Messinian) of central Italy. This species is represented by four articulated specimens and a caudal region of a fifth individual. Oreochromis lorenzoi, sp. nov. is the earliest confirmed representative of the genus Oreochromis, and it is the first European fossil cichlid. Oreochromis lorenzoi and additional examples from other fossil fishes provide evidence of faunal exchanges between Africa and the northern coasts of the Mediterranean during the Miocene. Paleoenvironmental implications are also discussed.

Sauroposeidon proteles, a new brachiosaurid sauropod, is represented by an articulated series of four mid-cervical vertebrae recovered from the Antlers Formation (Aptian-Albian) of southeastern Oklahoma. Most Early Cretaceous North American sauropod material has been referred to Pleurocoelus, a genus which is largely represented by juvenile material and is not well understood. Regardless of the status and affinities of Pleurocoelus, the new taxon is morphologically and proportionally distinct. Among well-known sauropod taxa, Sauroposeidon is most similar to Brachiosaurus; particularly noteworthy are the neural spines, which are set forward on the centra and are not bifurcate, and the extremely elongate cervical ribs. Sauroposeidon and Brachiosaurus also share a derived pattern of pneumatic vertebral ultrastructure and a mid-cervical transition point, at which neural spine morphology changes from very low (anteriorly) to very high (posteriorly). Autapomorphies of Sauroposeidon include posterior placement of the diapophyses, hypertrophied pneumatic fossae in the lateral faces of the neural spines and centra, and an extraordinary degree of vertebral elongation (e.g., C8 ϭ 1.25 m; 25% longer than Brachiosaurus). Additional sauropod material from the Early Cretaceous Cloverly Formation may be referrable to the new Oklahoma sauropod, which appears to be the last of the giant North American sauropods and represents the culmination of brachiosaurid trends towards lengthening and lightening of the neck.

We describe an associated skull and lower jaws of a new species of primitive skunk, Martinogale (subfamily Mephitinae), from the late Miocene Dove Spring Formation (late Clarendonian), Kern County, California. It is also the first occurrence of this genus in the Tertiary of the West Coast of North America. The new species is among the best-preserved primitive fossil skunks and represents one of the earliest members of the New World mephitines. As the smallest skunk so far known, the new Martinogale features some of the most primitive cranial and dental morphologies in mephitines. The new information permits a phylogenetic analysis of basal taxa from North America, which suggests a New World clade for all known fossil and living taxa from North and South America. We place this New World clade in a tribe (Mephitini) of its own. New World mephitines share the following derived characters: presence of a P4 parastyle, m1 hypoconid dominant in talonid, and presence of a lingual cingulum on lower canines. We further postulate that New World skunks are the result of a single immigration event, and the new California skunk is close to the origin of the New World skunks.

Elongate and asymmetric eggs of the oospecies Prismatoolithus levis occur regularly in the Upper Cretaceous Two Medicine Formation of western Montana. These eggs had previously been assigned to the ornithischian Orodromeus makelai, for both juvenile and adult remains are typically associated with these eggs. Reexamination of the embryos shows them to exhibit at least 24 apomorphies of the clades Dinosauria, Theropoda and Paraves. The embryos also display a pneumatic quadrate, closely placed basal tubera, a high tooth count, a metatarsal II much narrower than IV and a strongly constricted metatarsal III, all possible synapomorphies of the Troodontidae. Presence of large basal tubera and a broadly rounded anterior border of the maxillary fenestra permit assignment to Troodon formosus. Most but not all bones appear ossified, suggesting a developmental level comparable to stages 35-38 of avian embryos and a time approaching hatching. Embryos show a consistent level of development from one egg to another indicating synchronous hatching of the clutch. Embryonic Troodon exhibit long distal segments and radically different hindlimb proportions in comparison to adults. Orodromeus and other small vertebrate remains associated with Troodon egg horizons may represent prey of the adults during egg-laying and brooding.

Conflict between people and wildlife is a major issue in both wildlife conservation and rural development. In African rangelands, species such as African wild dogs (Lycaon pictus), cheetahs (Acinonyx jubatus), lions (Panthera leo), leopards (Panthera pardus), and spotted hyaenas (Crocuta crocuta) may kill livestock and are therefore themselves killed by local pastoralists. Such conflict has led to the extirpation of these species from many areas, and also impacts the livelihoods of local livestock farmers. To investigate the possibilities for coexistence of people, livestock, and large predators in community rangelands, we measured the effectiveness of traditional livestock husbandry in reducing depredation by wild carnivores, using a case-control approach. Different measures were effective against different predator species but, overall, the risk of predator attack by day was lowest for small herds, accompanied by herd dogs as well as human herders, grazing in open habitat. By night, the risk of attack was lowest for herds held in enclosures ('bomas') with dense walls, pierced by few gates, where both men and domestic dogs were present. Unexpectedly, the presence of scarecrows increased the risks of attack on bomas. Our findings suggest that improvements to livestock husbandry can contribute to the conservation and recovery of large carnivores in community rangelands, although other measures such as prey conservation and control of domestic dog diseases are also likely to be necessary for some species.

A new specimen of a sparassocynid didelphoid, consisting of a single skull, is described and analyzed. The specimen comes from the middle section of the Aisol Formation cropping out in Mendoza Province (Argentina) and constitutes the first marsupial hitherto described for the unit. The entire Aisol Formation was originally regarded as middle Miocene based on the fossil content. The discovery of new specimens, however, suggests that the stratigraphic level where the marsupial was found may have been deposited during the late Miocene (not older than Huayquerian times). The specimen studied here is identified as belonging to a new genus, Hesperocynus, of the family Sparassocynidae, Didelphoidea. A new combination is proposed for the already known species, H. dolgopolae (Reig 1958), previously recognized as a species of Thylatheridium Reig 1952. The new specimen from the Aisol Formation is assigned to the hypodigm of this taxon. The genus Hesperocynus encompasses small-sized carnivorous feeders as evidenced by their dental specializations and palate morphology; however, this taxon is more generalized than species of Sparassocynus, the other genus of the family. Sparassocynids have traditionally been considered the closest relatives of living didelphids. If this hypothesis is correct, then the sparassocynid clade has a long ghost lineage that covers at least 10 million years (as evidenced by the oldest known sparassocynid and didelphid remains). Sparassocynids and other didelphoids probably radiated after the global cooling event that occurred after the Eocene-Oligocene boundary.

The skeletal material of Wonambi naracoortensis has been re-examined, and used to test its phylogenetic relationships. The skeletal description, and the resulting data matrix, concentrates on characters that can be assessed by observation (on the associated material of Wonambi kept at the South Australian Museum). Macrostomatan affinities of Wonambi prove to be well supported. The taxon nests within Macrostomata, above Xenopeltis and Loxocemus.

The hadrosauroid dinosaur Pararhabdodon isonensis is known from partial cranial and postcranial material from the Maastrichtian of the south Pyrenean foredeep basin (northern Catalunya, Spain). We revise and emend the taxonomic history, stratigraphic context, osteology, and systematic position of this taxon. Our study leads us to rediagnose P. isonensis on the basis of a maxilla that combines an extremely elevated jugal joint with a subvertical and concave lateral surface of the maxilla ventral to the jugal joint, as well as a craniocaudally broad dorsal process; and a proximal half of the humerus medially offset 30º from its long axis. Our parsinomy heuristic analysis of P. isonensis and 22 other iguanodontoideans infers the phylogenetic position of the former as the sister taxon to Hadrosauridae (restricted here to the clade comprising Hadrosaurinae and Lambeosaurinae). One dentary, previously referred to P. isonensis, was collected at a site that is both stratigraphically and geographically separated from the type locality of P. isonensis. The dentary becomes the holotype of a new taxon, Koutalisaurus kohlerorum, on the basis of a uniquely elongated and medially projecting edentulous portion. This results in a distance between the symphysis and the lateral wall of the dentary that is three times the mediolateral breadth of the bone. K. kohlerorum shares with other hadrosauroids a tooth row that extends caudal to the apex of the coronoid process and, with Hadrosauridae, a tooth row that is, in occlusal view, straight and parallel to the lateral face of the dentary.