Total Clade Research Articles

The affinities of the Late Triassic Cryptovaranoides and the age of crown squamates.

Most living reptile diversity is concentrated in Squamata (lizards, including snakes), which have poorly known origins in space and time. Recently, †Cryptovaranoides microlanius from the Late Triassic of the United Kingdom was described as the oldest crown squamate. If true, this result would push back the origin of all major lizard clades by 30-65 Myr and suggest that divergence times for reptile clades estimated using genomic and morphological data are grossly inaccurate. Here, we use computed tomography scans and expanded phylogenetic datasets to re-evaluate the phylogenetic affinities of †Cryptovaranoides and other putative early squamates. We robustly reject the crown squamate affinities of †Cryptovaranoides, and instead resolve †Cryptovaranoides as a potential member of the bird and crocodylian total clade, Archosauromorpha. Bayesian total evidence dating supports a Jurassic origin of crown squamates, not Triassic as recently suggested. We highlight how features traditionally linked to lepidosaurs are in fact widespread across Triassic reptiles. Our study reaffirms the importance of critically choosing and constructing morphological datasets and appropriate taxon sampling to test the phylogenetic affinities of problematic fossils and calibrate the Tree of Life.

A new large tortoise from the early Oligocene (Arikareean NALMA) of Oaxaca, southern Mexico and its phylogenetic position within Pan-Testudinidae

ABSTRACT Pan-Testudinidae is the total clade of extant terrestrial tortoises, which includes extinct fossil members of their stem lineage. Members of this clade have a rather scarce fossil record in Mexico, and the few specimens known in scientific collections are poorly studied. Here, we described a new species of basal testudinid turtle, based on a single specimen from the early Oligocene deposits exposed in the marginal facies of the Chilapa Formation in Oaxaca, southern Mexico. The new taxon exhibits osteological characteristics that support its insertion as a basal Testudinidae. The phylogenetic relationships of the new turtle were assessed using a total evidence approach (morphological + molecular) in a global Pan-Testudinidae context using Implied Weighted Maximum Parsimony (IWMP), Standard Maximum Parsimony (SMP) and Bayesian Inference (BI). Although the BI consensus tree is not well resolved, the results obtained by IWMP and SMP retrieved its branching close to the root of Testudinidae. The differences between the topologies of the three phylogenetic analyses show that the position of several taxa within Testudinidae is affected by the phylogenetic analyses performed. The new taxon from Oaxaca, here reported, represents the first Palaeogene and the southernmost tortoise described from Mexico and the oldest Testudinidae known in the country.

The First Reconstruction of the Head Anatomy of a Cretaceous Insect, †Gerontoformica gracilis(Hymenoptera: Formicidae), and the Early Evolution of Ants

AbstractThe fossil record allows a unique glimpse into the evolutionary history of organisms living on Earth today. We discovered a specimen of the stem group ant †Gerontoformica gracilis (Barden and Grimaldi, 2014) in Kachin amber with near-complete preservation of internal head structures, which we document employing µ-computed-tomography-based 3D reconstructions. We compare †Gerontoformica to four outgroup taxa and four extant ant species, employing parsimony and Bayesian ancestral state reconstruction to identify morphological differences and similarities between stem and crown ants and thus improve our understanding of ant evolution through the lens of head anatomy. Of 149 morphological characters, 87 are new in this study, and almost all applicable to the fossil. †Gerontoformica gracilis shares shortened dorsal tentorial arms, basally angled pedicels, and the pharyngeal gland as apomorphies with other total clade Formicidae. Retained plesiomorphies include mandible shape and features of the prepharynx. Implications of the reconstructed transitions especially for the ant groundplan are critically discussed based on our restricted taxon sampling, emphasizing the crucial information derived from internal anatomy which is applied to deep time for the first time. Based on the falcate mandible in †Gerontoformica and other Aculeata, we present hypotheses for how the shovel-shaped mandibles in crown Formicidae could have evolved. Our results support the notion of †Gerontoformica as ‘generalized’ above-ground predator missing crucial novelties of crown ants which may have helped the latter survive the end-Cretaceous extinction. Our study is an important step for anatomical research on Cretaceous insects and a glimpse into the early evolution of ant heads.

New Diminutive Eocene Lizard Reveals High K-Pg Survivorship and Taxonomic Diversity of Stem Xenosaurs in North America

We describe a new diminutive early Eocene lizard, Blutwurstia oliviae, gen. et sp. nov., on the basis of associated cranial and postcranial remains from the Clarks Fork Basin of Wyoming. Results from phylogenetic analyses suggest that B. oliviae is on the stem of knob-scaled lizards (Xenosaurus), a relict extant clade of specialized, stenotopic crevice-dwellers from Mexico and Central America. Results further suggest that B. oliviae is basal to all other previously described pan-xenosaurs (members of Pan-Xenosaurus, the total clade of Xenosaurus) except species of Entomophontes, to which it is closely related. Given that B. oliviae and Entomophontes are known from a limited fossil record, with only one recovered element (the maxilla) in common, the level of support for this relationship is surprisingly high. We use a posteriori time-calibrated trees and ghost lineages (maximum parsimony) and divergence time estimates under the fossilized birth-death process (Bayesian inference) to infer patterns of extinction across the Cretaceous-Paleogene (K-Pg) boundary in Pan-Xenosaurus, including those consistent with pseudoextinction. Whereas the fossil record documents a single lineage in the latest Cretaceous, results from analyses using these analytical methods suggest that three or more species existed, with high survivorship across the K-Pg boundary. The surviving lineages were apparently present at proximal to intermediate distance from the Chicxulub impact site, thought to have a causal relationship with extinctions across the K-Pg boundary. The premaxilla and dorsal vertebrae of E. incrustatus and B. oliviae, respectively, independently suggest that each of these taxa had a depressed body form consistent with extant crevice-dwelling squamates, which may have played a role in the high survivorship of pan-xenosaur lineages across the K-Pg boundary.

Evidence for the evolution of eusociality in stem ants and a systematic revision of †Gerontoformica (Hymenoptera: Formicidae)

Abstract It is generally assumed that Cretaceous stem ants were obligately eusocial, because of the presence of wingless adult females, yet the available evidence is ambiguous. Here, we report the syninclusion of a pupa and adult of a stem ant species from Mid-Cretaceous amber. As brood are immobile, the pupa was likely to have been transported by an adult. Therefore, the fossil substantiates the hypothesis that wingless females were cooperators, thus these were true ‘workers’. Re-examination of all described Cretaceous ant species reveals that winged–wingless diphenism – hence a variable dispersal capacity – may have been ancestral to the total clade of the ants, and that highly specialized worker-specific phenotypes evolved in parallel between the stem and crown groups. The soft-tissue preservation of the fossil is exceptional, demonstrating the possibility of analysing the development of the internal anatomy in stem ants. Based on the highest-resolution µ-CT scans of stem ants to date, we describe †Gerontoformica sternorhabda sp. nov., redescribe †G. gracilis, redefine the species group classification of †Gerontoformica, and provide a key to the species of the genus. Our work clarifies the species boundaries of †Gerontoformica and renders fossils relevant to the discussion of eusocial evolution in a way that has heretofore been intractable.

The Evolution and Fossil Record of Palaeognathous Birds (Neornithes: Palaeognathae)

The extant diversity of the avian clade Palaeognathae is composed of the iconic flightless ratites (ostriches, rheas, kiwi, emus, and cassowaries), and the volant tinamous of Central and South America. Palaeognaths were once considered a classic illustration of diversification driven by Gondwanan vicariance, but this paradigm has been rejected in light of molecular phylogenetic and divergence time results from the last two decades that indicate that palaeognaths underwent multiple relatively recent transitions to flightlessness and large body size, reinvigorating research into their evolutionary origins and historical biogeography. This revised perspective on palaeognath macroevolution has highlighted lingering gaps in our understanding of how, when, and where extant palaeognath diversity arose. Towards resolving those questions, we aim to comprehensively review the known fossil record of palaeognath skeletal remains, and to summarize the current state of knowledge of their evolutionary history. Total clade palaeognaths appear to be one of a small handful of crown bird lineages that crossed the Cretaceous-Paleogene (K-Pg) boundary, but gaps in their Paleogene fossil record and a lack of Cretaceous fossils preclude a detailed understanding of their multiple transitions to flightlessness and large body size, and recognizable members of extant subclades generally do not appear until the Neogene. Despite these knowledge gaps, we combine what is known from the fossil record of palaeognaths with plausible divergence time estimates, suggesting a relatively rapid pace of diversification and phenotypic evolution in the early Cenozoic. In line with some recent authors, we surmise that the most recent common ancestor of palaeognaths was likely a relatively small-bodied, ground-feeding bird, features that may have facilitated total-clade palaeognath survivorship through the K-Pg mass extinction, and which may bear on the ecological habits of the ancestral crown bird.

The oldest Cenozoic ant fossil: †Tyrannomecia gen. nov. (Formicidae: Myrmeciinae) from the Palaeocene Menat Formation (France)

ABSTRACT A new genus and species of myrmeciine ants, also called bulldog ants, is described and illustrated from the Palaeocene of Menat (France) as Tyrannomecia inopinata gen. et sp. nov. This new taxon represents the oldest representative of the subfamily and provides the oldest calibration point for the total clade Myrmeciinae. It shows the apomorphic characters used to define the Myrmeciinae: mandibles elongate such that their length is three-quarters or more of head length, third abdominal segment (AIII) substantially smaller than the fourth abdominal segment (AIV), and with its height distinctly less than that of the fourth one. This new genus is easily differentiated from all the other myrmeciine ants owing to its petiole with a conspicuous tooth located dorsally on the posterior declivity, and is considered to belong to the stem-Myrmeciinae. Aside from the calibration aspects, this new taxon, possessing a hunter morphology, is used to discuss implications for the recovery of ants after the K/Pg.

Dating the origin and diversification of Pan-Chelidae (Testudines, Pleurodira) under multiple molecular clock approaches

Pan-Chelidae (Testudines, Pleurodira) is a group of side-necked turtles with a currently disjointed distribution in South America and Australasia and characterized by two morphotypes: the long-necked and the short-necked chelids. Both geographic groups include both morphotypes, but different phylogenetic signals are obtained from morphological and molecular data, suggesting the monophyly of the long-necked chelids or the independent evolution of this trait in both groups. In this paper, we addressed this conflict by compiling and editing available molecular and morphological data for Pan-Chelidae, and performing phylogenetic and dating analyses over the individual and the combined datasets. Our total-evidence phylogenetic analysis recovered the clade Chelidae as monophyletic and as sister group of a clade of South American extinct chelids; furthermore Chelidae retained inside the classical molecular structure with the addition of extinct taxa in both the Australasian and the South American clades. Our dating results suggest a Middle Jurassic origin for the total clade Pan-Chelidae, an Early Cretaceous origin for Chelidae, a Late Cretaceous basal diversification of both geographic clades with the emergence of long-necked lineages, and an Eocene diversification at genera level, with the emergence of some species before the final breakup of Southern Gondwana and the remaining species after this event.

The first known fossil Uma: ecological evolution and the origins of North American fringe-toed lizards

BackgroundFossil evidence suggests that extant North American lizard genera (north of Mexico) evolved during the Miocene. Although fossils of the clade Phrynosomatidae (spiny lizards and sand lizards) have been reported, there have been no previously described fossils of the fringe-toed sand lizards (Uma). In the extant biota, Uma inhabit arid deserts, and members of the western clade of Uma are restricted to sand dunes or other habitats containing fine-grained sand.ResultsI describe the first known fossil of Uma and refer the fossil to the total clade of Uma with an apomorphy-based diagnosis. The fossil is a partial premaxilla that was found in the Miocene strata of the Dove Spring Formation of southern California, dating to 8.77 Ma. The paleoenvironment of the Dove Spring Formation was semiarid and contained ephemeral streams that facilitated deposition, and there is no evidence of sand dune deposits in the strata containing the locality from which the Uma fossil was found. Divergence time analyses of a concatenated molecular dataset with four fossil calibrations support a Neogene origin of the total clade of Uma and of the crown clade of Uma. Those analyses also estimated a Neogene divergence between Uma scoparia and the Uma notata complex. Multispecies coalescent analyses with one fossil calibration inferred a Paleogene origin for the total clade of Uma and a Pliocene or Pleistocene divergence between Uma scoparia and the Uma notata complex. The fossil and the total and crown clades of Uma precede the evolution of modern desert ecosystems in the southwestern United States and northern Mexico by millions of years.ConclusionsThe total clade and the crown clade of Uma were not restricted to arid deserts throughout their evolutionary histories. I demonstrate that an apomorphy-based diagnosis can be used to identify fossils of isolated skeletal elements for at least one clade of phrynosomatid lizard, and suggest exercising caution when using environmental tolerances of extant taxa to hypothesize paleoecological reconstructions.

New Early Miocene Material of Iberictis, the Oldest Member of the Wolverine Lineage (Carnivora, Mustelidae, Guloninae)

We describe new dental remains of the genus Iberictis (Carnivora: Mustelidae) from the late early Miocene of the Iberian Peninsula. The new fossils of Iberictis azanzae from Artesilla (16.5–16.3 Ma, MN4; Calatayud-Teruel Basin, Zaragoza, Spain) add important morphological information about this species. Material from another species, Iberictis buloti, is described from els Casots (16.5–16.3 Ma, MN4; Valles-Penedes Basin, Barcelona, Spain). This material constitutes the most complete sample of Iberictis and the first record of I. buloti in the Iberian Peninsula. Our analyses confirm the taxonomic validity of both species, and confirm the more plesiomorphic status of I. buloti compared to I. azanzae. Re-examination of large mustelid Miocene genera (Dehmictis, Ekorus, Eomellivora, Hoplictis, Iberictis, Ischyrictis, and Plesiogulo) and their inclusion for the first time in a cladistic analysis indicate that Iberictis is the sister taxon of Plesiogulo, and that these genera constitute the sister group of the extant wolverine (Gulo gulo). Our analysis thus confirms a close relationship between the early Miocene Iberictis, the late Miocene Plesiogulo, and the Plio-Pleistocene Gulo. Iberictis is the oldest member of Gulonini, the total clade of wolverines, thereby tracking the fossil record of this clade back to the early Miocene. We further propose a new systematic arrangement for the aforementioned large Miocene mustelids into the subfamilies Guloninae, Mellivorinae, and Mustelinae.

Ecological and Ecomorphological Specialization Are Not Associated with Diversification Rates in Muroid Rodents (Rodentia: Muroidea)

Multiple diversification rate shifts explain uneven clade richness in muroid rodents. Previous muroid studies have shown that extrinsic factors, notwithstanding ecological opportunity, are poor predictors of clade diversity. Here, we use a 297-muroid species chronogram that is sampled proportional to total clade diversity, along with various trait-dependent diversification approaches to investigate the association between diversification rates with intrinsic attributes—diet, habitat, body mass, and relative tail length. We found some association between both dietary specialization and body mass, as well as between habitat specialization with relative tail lengths using phylogenetic analyses of variance. However, there was no significant association between diversification rates with the evolution of these traits in muroid rodents. We also show that several of the state-dependent diversification approaches are highly susceptible to Type I error—a result that is in accordance with recent criticisms of these methods. Finally, we discuss several potential causes for the lack of association between the examined trait data with diversification rates, ranging from methodological biases (e.g. method conservativism) to biology (e.g. behavioral plasticity and ecological opportunism of muroid rodents).

Total evidence analysis and body size evolution of extant and extinct tortoises (Testudines: Cryptodira: Pan-Testudinidae).

Testudinidae (tortoises) is an extant clade of terrestrial turtles of worldwide distribution and with a rich fossil record that provides an exceptional context for studying their evolutionary history. Because of the lack of global phylogenetic analyses integrating extinct taxa, our current knowledge of the relationships of the total clade of Testudinidae is rather poor. To resolve this issue, we performed the first total evidence analysis of Pan-Testudinidae. The total evidence trees are congruent with the molecular topology and agree on the dichotomy of derived Testudinidae (=Testudininae; Converted Clade Name) into two previously recognized major clades, Testudona and Geochelona (New Clade Name). The integration of extinct taxa into the analysis allowed the stratigraphic fit of the total evidence trees, indicating that crown Testudininae, Testudona and Geochelona all originated by the Late Eocene, in agreement with recent molecular estimates. Ghost lineage analysis indicates high diversification in the Late Eocene and in the Miocene. The age of crown Testudo is Late Miocene, again in accordance with some molecular dates. Phylogenetic placement of fossils demonstrates that giant body size independently evolved in multiple continental mainland taxa and confirms recent results deduced from living taxa-giantism in Testudinidae is not linked to the insular effect. An unexpected outcome is the recovery of miniaturization in Testudona (<30cm carapace length) that emerged sometime between the Oligocene and Early Miocene. No clear correlation between body size evolution and climate is apparent, but increased taxon sampling may nevertheless demonstrate the role of cooling and warming as one of many influential variables.

A Review of the Fossil Record of Turtles of the CladePan-Chelidae

Abstract Turtles of the total Clade Pan-Chelidae have a relatively poor fossil record, which is completely restricted from the Early Cretaceous to Recent of South America and Australasia. The clade is expected to have formerly inhabited Antarctica as well. The phylogenetic relationships of extant pan-chelids remain poorly resolved, notably because there are conflicting signals between morphological and molecular data. The ecology of fossil pan-chelids appears to have been similar to that of their extant relatives. A taxonomic review of the group concluded that of 45 named taxa, 22 are nomina valida, 6 are nomina invalida and 15 are nomina dubia, whereas the final 2 are rendered non-testudinate through the designation of lectotypes.

Genetic diversity and antigenicity variation of Babesia bovis merozoite surface antigen-1 (MSA-1) in Thailand

Babesia bovis, an intraerythrocytic protozoan parasite, causes severe clinical disease in cattle worldwide. The genetic diversity of parasite antigens often results in different immune profiles in infected animals, hindering efforts to develop immune control methodologies against the B. bovis infection. In this study, we analyzed the genetic diversity of the merozoite surface antigen-1 (msa-1) gene using 162 B. bovis-positive blood DNA samples sourced from cattle populations reared in different geographical regions of Thailand. The identity scores shared among 93 msa-1 gene sequences isolated by PCR amplification were 43.5–100%, and the similarity values among the translated amino acid sequences were 42.8–100%. Of 23 total clades detected in our phylogenetic analysis, Thai msa-1 gene sequences occurred in 18 clades; seven among them were composed of sequences exclusively from Thailand. To investigate differential antigenicity of isolated MSA-1 proteins, we expressed and purified eight recombinant MSA-1 (rMSA-1) proteins, including an rMSA-1 from B. bovis Texas (T2Bo) strain and seven rMSA-1 proteins based on the Thai msa-1 sequences. When these antigens were analyzed in a western blot assay, anti-T2Bo cattle serum strongly reacted with the rMSA-1 from T2Bo, as well as with three other rMSA-1 proteins that shared 54.9–68.4% sequence similarity with T2Bo MSA-1. In contrast, no or weak reactivity was observed for the remaining rMSA-1 proteins, which shared low sequence similarity (35.0–39.7%) with T2Bo MSA-1. While demonstrating the high genetic diversity of the B. bovis msa-1 gene in Thailand, the present findings suggest that the genetic diversity results in antigenicity variations among the MSA-1 antigens of B. bovis in Thailand.

A Review of the Fossil Record of Turtles of the CladePan-Kinosternoidea

Abstract Turtles of the total clade Pan-Kinosternoidea have a relatively poor fossil record that extends back to the Late Cretaceous (Campanian). The clade is found only in North America during its early history, but dispersed to Central America no later than the Miocene and to South America no later than the Pleistocene. Ancestral pan-kinosternoids were likely aquatic, bottom-walking omnivores or carnivores that preferred low-energy freshwater habitats. The Pan-Dermatemys lineage is often recovered in more fluvial habitats, and some are specialized to feed on aquatic vegetation. Alternatively, many representatives of Kinosternon evolved specializations (e.g., plastral lobe kinesis) that allowed them to successfully inhabit and disperse across more terrestrial habitats such as savannas and floodplains. A taxonomic review of the group concludes that of 42 named taxa, 27 are nomina valida (including two species of the controversial taxon Planetochelys), 14 are nomina invalida and only one a nomen dubium.

A Review of the Fossil Record of Turtles of the CladePan-Chelydridae

Turtles of the total clade Pan-Chelydridae have a relatively sparse fossil record that reaches back to the Late Cretaceous (Santonian). The clade was only present in North America during the Cretaceous but spread along unclear routes to Asia and Europe during the Paleocene, only to go extinct on those continents by the end of the Pliocene. Final dispersal to South America took place at some time during the late Neogene. The ecology of stem chelydrids seems to have been similar to that of the extant Chelydra serpentina, although more primitive representatives were more molluscivorous as inferred from their broader triturating surfaces. Current phylogenies only recognize five internested clades: Pan-Chelydridae, Chelydridae, Chelydropsis, Chelydra and Macrochelys. A taxonomic review of the group concludes that of 31 named fossil taxa, 8 are nomina valida, 10 are nomina invalida, 9 are nomina dubia, 1 is a nomen nudum and 1 is a regular, unavailable name.

Phylogenetic relationships of †Luisiella feruglioi (Bordas) and the recognition of a new clade of freshwater teleosts from the Jurassic of Gondwana.

BackgroundTeleosts constitute more than 99 % of living actinopterygian fishes and fossil teleosts have been studied for about two centuries. However, a general consensus on the definition of Teleostei and the relationships among the major teleostean clades has not been achieved. Our current ideas on the origin and early diversification of teleosts are mainly based on well-known Mesozoic marine taxa, whereas the taxonomy and phylogenetic relationships of many Jurassic continental teleosts are still poorly understood despite their importance to shed light on the early evolutionary history of this group. Here, we explore the phylogenetic relationships of the Late Jurassic (Oxfordian – Tithonian) freshwater †Luisiella feruglioi from Patagonia, in a comprehensive parsimony analysis after a thorough revision of characters from previous phylogenetic studies on Mesozoic teleosts.ResultsWe retrieved †Luisiella feruglioi as the sister taxon of the Late Jurassic †Cavenderichthys talbragarensis, both taxa in turn forming a monophyletic group with the Early Cretaceous †Leptolepis koonwarri. This new so far exclusively Gondwanan freshwater teleost clade, named †Luisiellidae fam. nov. herein, is placed outside crown Teleostei, as a member of the stem-group immediately above the level of †Leptolepis coryphaenoides. In addition, we did not retrieve the Late Jurassic †Varasichthyidae as a member of †Crossognathiformes. The position of †Crossognathiformes within Teleocephala is confirmed whereas †Varasichthyidae is placed on the stem.ConclusionsThe general morphology of luisiellids is that of basal, stem Teleocephala; however, most of their synapomorphies have evolved independently in teleocephalans. Similarly, the resemblance between varasichthyids and crossognathiforms might be due to parallel evolution. In accordance to most teleostean phylogenies, our analysis shows that a major morphological change occurred along the stem line and are currently recorded at the level of †Leptolepis coryphaenoides. A stem-based total clade Teleostei has been accepted for this work.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0551-6) contains supplementary material, which is available to authorized users.

Fossil lizard from central Europe resolves the origin of large body size and herbivory in giant Canary Island lacertids

The endemic Canary Island lizard clade Gallotia, which includes the largest members of Europe's dominant reptile group, Lacertidae, is one of the classic examples of insular gigantism. For the first time we use fossil data to test the evolutionary reasons for the association between gigantism and herbivory. We describe an almost completely preserved skeleton of Janosikia ulmensis comb. nov. from the early Miocene of Ulm, Germany (MN 2a, ∼ 22 Mya). We show that this species and Oligocene Pseudeumeces cadurcensis (Filhol, 1877) are in fact crown lacertids, and the first known pre-Quaternary record of the total clade of Gallotia. Pseudeumeces confirms the early origin of crown Lacertidae in the Palaeogene of Europe. More importantly, these fossil taxa show that large body size was already achieved on the European mainland by the early Miocene. Furthermore, Pseudeumeces and Janosikia were faunivorous, thus demonstrating that insularity, not large body size, was crucial to the evolution of herbivory in this lineage. Body size change in Gallotia was more complex than previously thought, encompassing size increase [e.g. in the extinct Gallotia goliath (Mertens, 1942)], but more commonly involving miniaturization. The physical environment may play a crucial role in modulating the evolution of body size in this natural laboratory. © 2015 The Linnean Society of London

Fossil calibration dates for molecular phylogenetic analysis of snakes 1: Serpentes, Alethinophidia, Boidae, Pythonidae

Snakes possess a dense fossil record through the Late Cretaceous and Cenozoic and are an important clade for studies of molecular phylogenetics. The use of the snake fossil record has historically been a limited and inaccurate source of temporal data in molecular studies due to taxonomic and phylogenetic ambiguities. Here I provide 10 fossil calibration dates for phylogenetic analysis of higher-order interrelationships of snakes. Calibration points include apomorphy-based systematic justifications and precise dates for hard minimum divergence timings. Calibrated nodes are for the snake total clade, Alethinophidia, and boid and pythonid taxa. Hard minimum divergence timings range from earliest late Cretaceous to middle Miocene. These dates provide precise minima for constraining the early evolutionary history of Serpentes. Comparisons of phylogenetically justified calibrations with published studies that employed form-taxon assignments suggests greatly younger divergences for justified nodes and indicates that deep-time divergence estimates that have been correlated with tectonic histories may be considerably too old and reliant on presumptions of Early Cretaceous Gondwanan vicariance as a mechanism of speciation. Jason J. Head. Department of Earth and Atmospheric Sciences and Nebraska State Museum of Natural History University of Nebraska-Lincoln, Lincoln, NE 68588-04340. Jhead2@unl.edu.

A Review of the Fossil Record of Turtles of the CladePan-Carettochelys

Turtles of the total clade Pan-Carettochelys have a relatively poor fossil record that extends from the Early Cretaceous. The clade is only found in Asia during the Cretaceous, but spreads to Europe and North America during the Eocene. Neogene finds are restricted to Europe, Africa and Australia, whereas the only surviving species, Carettochelys insculpta, lives in New Guinea and the Northern Territories of Australia. The ecology of fossil pan-carettochelyids appears similar to that of the extant C. insculpta, although more primitive representatives were likely less adapted to brackish water. Current phylogenies only recognize three internested clades: Pan-Carettochelys, Carettochelyidae and Carettochelyinae. A taxonomic review of the group concludes that of 25 named taxa, 13 are nomina valida, 7 are nomina invalida, 3 are nomina dubia, and 2 are nomina nuda.