Jeremy E. Martin

NEW MATERIAL OF THE LATE CRETACEOUS GLOBIDONTAN ACYNODON IBEROCCITANUS (CROCODYLIA) FROM SOUTHERN FRANCE

Abstract Two exquisitely preserved specimens from the Late Cretaceous of southeastern France, together with less complete material from southwestern France, allow the most complete description of the cranial morphology of Acynodon iberoccitanus. The extremely brevirostrine condition associated with a unique dentition might indicate derived dietary behavior for Acynodon. New characters were coded in a previously published matrix. In this context, Acynodon is placed in a polytomy at the base of Globidonta. As an early European form, the position of Acynodon implies that no biogeographic models can be favoured to explain alligatoroid and globidontan migrations between North America and Europe.

First Clarkforkian equivalent Land Mammal Age in the latest Paleocene basal Sparnacian facies of Europe: fauna, flora, paleoenvironment and (bio)stratigraphy.

The Paleocene-Eocene Thermal Maximum (PETM) is correlated with the first occurrences of earliest modern mammals in the Northern Hemisphere. The latest Paleocene Clarkforkian North American Land Mammal Age, that has yielded rodents and carnivorans, is the only exception to this rule. However, until now no pre-PETM localities have yielded modern mammals in Europe or Asia. We report the first Clarkforkian equivalent Land Mammal Age in the latest Paleocene deposits of the basal Sparnacian facies at Rivecourt, in the north-central part of the Paris Basin. The new terrestrial vertebrate and macroflora assemblages are analyzed through a multidisciplinary study including sedimentologic, stratigraphic, isotopic, and palynological aspects in order to reconstruct the paleoenvironment and to evaluate biochronologic and paleogeographic implications. The mammals are moderately diverse and not abundant, contrary to turtles and champsosaurs. The macroflora is exceptional in preservation and diversity with numerous angiosperms represented by flowers, fruits, seeds and wood preserved as lignite material, revealing an abundance of Arecaceae, Betulaceae, Icacinaceae, Menispermaceae, Vitaceae and probably Cornaceae. Results indicate a Late Paleocene age based on carbon isotope data, palynology and vertebrate occurrences such as the choristoderan Champsosaurus, the arctocyonid Arctocyon, and the plesiadapid Plesiadapis tricuspidens. However, several mammal species compare better with the earliest Eocene. Among these, the particular louisinid Teilhardimys musculus, also recorded from the latest Paleocene of the Spanish Pyrenees, suggests a younger age than the typical MP6 reference level. Nevertheless, the most important aspect of the Rivecourt fauna is the presence of dental remains of a rodent and a “miacid” carnivoran, attesting to the presence of two modern mammalian orders in the latest Paleocene of Europe. Interestingly, these two groups are also the only modern groups recorded from the latest Paleocene of North America, making Rivecourt the first direct equivalent to the Clarkforkian Land Mammal Age outside of North America.

Palaeoenvironmental significance of Toarcian black shales and event deposits from southern Beaujolais, France

New sedimentological, biostratigraphical and geochemical data recording the Toarcian OceanicAnoxicEvent(T-OAE)arereportedfromamarginalmarinesuccessioninsouthernBeaujolais, France. The serpentinum and bifrons ammonite zones record black shales with high (1-10 wt %) total organic carbon contents (TOC) and dysoxia-tolerant benthic fauna typical of the Schistes Carton facies well documented in contemporaneous nearby basins. The base of the serpentinum ammonite zone, however, differs from coeval strata of most adjacent basinal series in that it presents several massive storm beds particularly enriched in juvenile ammonites and the dysoxia-tolerant, miniaturized gastropod Coelodiscus. This storm-dominated interval records a marked negative 5 ‰ carbonate and organic carbon isotope excursion being time-equivalent with that recording storm- and mass flow-deposits in sections of the Lusitanian Basin, Portugal, pointing to the existence of a major tempestite/turbidite event over tropical areas during the T-OAE. Although several explanations remain possible at present, we favour climatically induced changes in platform morphology and storm activity as the main drivers of these sedimentological features. In addition, we show that recent weathering, most probably due to infiltration of O2-rich meteoric water, resulted in the preferential removal of 12 C-enriched organic carbon, dramatic TOC loss and total destruction of the lamination of the black shale sequence over most of the studied exposure. These latter observations imply that extreme caution should be applied when interpreting the palaeoenvironmental significance of sediments lacking TOC enrichment and lamination from outcrops with limited surface exposures.

Cranial morphology of Theriosuchus sympiestodon (Mesoeucrocodylia, Atoposauridae) and the widespread occurrence of Theriosuchus in the Late Cretaceous of Europe

Abstract We present a detailed morphological description of the type-locality cranial material of Theriosuchus sympiestodon Martin, Rabi, and Csiki, 2010 from the Maastrichtian Densuş-Ciula Formation of the Haţeg Basin, Romania together with new material of isolated cranial elements and teeth from various sites of the same general area. The recognition of several individuals of distinct sizes allows for an assessment of ontogenetic variation in this taxon. New material, consisting of isolated teeth and an incomplete maxilla with in situ teeth, coming from various late Campanian/early Maastrichtian sites in southern France is referable to ?Theriosuchus sp. and hints to a rare but widespread distribution of Theriosuchus in the Late Cretaceous European archipelago.

The maxillary depression of Pholidosauridae: an anatomical study

Goniopholidids and pholidosaurids are common crocodilians in Late Jurassic and Early Cretaceous freshwater environments in many parts of the world, although evidence that goniopholidids ever reached Gondwanan regions needs to be substantiated. In the ‘mid’-Cretaceous, some pholidosaurids (Terminonaris, Oceanosuchus) became adapted to life in the sea, a domain that goniopholidids apparently never occupied. Whereas goniopholidids were mainly mesorostral forms, pholidosaurids were longirostral. There is currently no consensus about the phylogenetic relationships between goniopholidids and pholidosaurids. They have been considered as closely related on the basis of various shared characters (Buffetaut, 1982), but in some recent phylogenetic analyses (e.g., Jouve et al., 2006; Jouve, 2009; Pol et al., 2009) at least some pholidosaurids cluster with other longirostral forms such as dyrosaurids and thalattosuchians, which may suggest that the family Pholidosauridae is not monophyletic. Nevertheless, a number of characters uniting Pholidosauridae have recently been proposed (Hua et al., 2007), but were not tested in a phylogenetic framework. On the other hand, only one unambiguous character diagnoses the clade Goniopholididae in phylogenetic studies: the presence of a depression on the posterior end of the maxilla, described as the ‘depression maxillaire’ (maxillary depression) by Buffetaut (1982; see also Lauprasert et al., 2007). On this basis, Goniopholididae is accepted as a monophyletic entity comprising the generaCalsoyasuchus,Goniopholis,Eutretauranosuchus, Siamosuchus, and Sunosuchus (Tykoski et al., 2002; Lauprasert et al., 2007; Smith et al., 2010), thus agreeing with pre-cladistic views (Buffetaut, 1982). Functionally, the maxillary depression may have housed a sensory organ helping to localize and capture prey in the aquatic environment (Brandalise de Andrade, 2009). Here, we report for the first time the presence of a maxillary depression in Pholidosauridae. Its morphology and position is for the first time described in taxa where the maxillojugal area is preserved. Implications for a close relationship between Goniopholididae and Pholidosauridae are discussed on the basis of this previously overlooked character. Institutional Abbreviations—AMNH, American Museum of Natural History, New York, U.S.A.; BYU, Brigham Young University, Provo, Utah, U.S.A.; CHE, Universite Lyon 1, Lyon, France, specimen from Cherves de Cognac; CMNH, Cleveland Museum of Natural History, Cleveland, Ohio, U.S.A.; DORCM, Dorset County Museum, Dorchester, United Kingdom; MNHN, Museum National d’Histoire Naturelle, Paris, France;MNN, Musee National du Niger, Niamey, Republique du Niger; NHMUK, The Natural History Museum, London, United Kingdom.

Magnesium stable isotope ecology using mammal tooth enamel

Significance The diet of fossil organisms can be inferred through isotopic analysis of skeletal tissues, largely assessed using isotopic and elemental systems such as carbon isotopes (δ13C) and strontium/calcium (Sr/Ca) and barium/calcium (Ba/Ca) concentration ratios. In the case of complex dietary habits such as omnivory, these systems must be used jointly together with new proxies. Based on the expectation that fractionation of bio-essential metals occurs during metabolism, we explore the isotopic variability of magnesium (δ26Mg) in tooth enamel sampled from an assemblage of modern mammals. We demonstrate that δ26Mg increases from herbivores to higher-level consumers, discriminating most of the identified trophic steps. This, combined with δ13C, Ba/Ca, and/or δ44Ca might prove useful in paleodietary studies. Geochemical inferences on ancient diet using bone and enamel apatite rely mainly on carbon isotope ratios (δ13C) and to a lesser extent on strontium/calcium (Sr/Ca) and barium/calcium (Ba/Ca) elemental ratios. Recent developments in nontraditional stable isotopes provide an unprecedented opportunity to use additional paleodietary proxies to disentangle complex diets such as omnivory. Of particular relevance for paleodietary reconstruction are metals present in large quantity in bone and enamel apatite, providing that biologically mediated fractionation processes are constrained. Calcium isotope ratios (δ44Ca) meet these criteria but exhibit complex ecological patterning. Stable magnesium isotope ratios (δ26Mg) also meet these criteria but a comprehensive understanding of its variability awaits new isotopic data. Here, 11 extant mammal species of known ecology from a single locality in equatorial Africa were sampled for tooth enamel and, together with vegetation and feces, analyzed for δ26Mg, δ13C, Sr/Ca, and Ba/Ca ratios. The results demonstrate that δ26Mg incorporated in tooth enamel becomes heavier from strict herbivores to omnivores/faunivores. Using data from experimentally raised sheep, we suggest that this 26Mg enrichment up the trophic chain is due to a 26Mg enrichment in muscle relative to bone. Notably, it is possible to distinguish omnivores from herbivores, using δ26Mg coupled to Ba/Ca ratios. The potential effects of metabolic and dietary changes on the enamel δ26Mg composition remain to be explored but, in the future, multiproxy approaches would permit a substantial refinement of dietary behaviors or enable accurate trophic reconstruction despite specimen-limited sampling, as is often the case for fossil assemblages.

Marine vertebrate remains from the Toarcian-Aalenian succession of southern Beaujolais, Rhone, France

A previously undocumented marine vertebrate fauna comprising ichthyosaur, plesiosaur, marine crocodilian and fish remains from the Toarcian-Aalenian succession at Lafarge quarry, southern Beaujolais (Rhone, France) is described on the basis of both historical collections and new discoveries. The taxonomic composition of the Lafarge quarry marine vertebrate assemblage highlights its cosmopolitan nature and strong relationships with taxa known from elsewhere in Europe. Several groups are recorded for the first time in the Toarcian-Aalenian succession of France, implying new palaeobiogeographic interpretations and prompting discussion of marine amniote diversity during this interval.

Surviving a potentially lethal injury? Bite mark and associated trauma in the vertebra of a dyrosaurid crocodilian

Abstract A vertebral centrum belonging to a dyrosaurid, a marine crocodilian recovered from the late Paleocene of Niger, bears a large ovoid and deep puncture on its lateral flank. This mark is identified as a wound inflicted by the bite of another crocodilian. Although the wound shows evidence of healing, the vertebral centrum has been severely damaged and deformed. It provides a rare direct evidence of the aggressive interactions taking place between these now extinct marine reptiles, the largest known marine predators of their time before the rise of the archeocetes.

Gavialis from the Pleistocene of Thailand and Its Relevance for Drainage Connections from India to Java

Background The genus Gavialis comprises a single living but endangered species, G. gangeticus, as well as fossil species recorded in the Miocene to Pleistocene deposits of the Indian subcontinent. The genus is also represented in the Pleistocene deposits of Java by the species G. bengawanicus, which was recently recognized to be valid. Surprisingly, no detailed report of the genus exists between these two provinces and the recent evolutionary history of Gavialis is not understood. Methodology/Principal Findings We report new material consisting of skull and mandibular remains of Gavialis from the Early Pleistocene of Khok Sung, Nakhon Ratchasima Province, northeastern Thailand. The Gavialis material described herein is attributed to Gavialis cf. bengawanicus and sheds new light on the occurrence of the genus in mainland SE Asia. Conclusions/Significance Comparison of this new material with other species referred to the genus Gavialis led us to preliminary restrict the content of the genus to three species, namely G. gangeticus Gmelin, G. bengawanicus Dubois and G. lewisi Lull. The occurrence of G. cf. bengawanicus in Thailand allows us to propose a scenario for the dispersal of Gavialis from Indo-Pakistan to Indonesia, thus bridging a geographical gap between these two provinces. Dispersal by sea appears a less likely possibility than dispersal through fluvial drainages.