Tiago R. Simões

Giant taxon-character matrices: quality of character constructions remains critical regardless of size

Giant morphological data matrices are increasingly common in cladistic analyses of vertebrate phylogeny, reporting numbers of characters never seen or expected before. However, the concern for size is usually not followed by an equivalent, if any, concern for character construction/selection criteria. Therefore, the question of whether quantity parallels quality for such influential works remains open. Here, we provide the largest compilation known to us of character construction methods and criteria, as derived from previous studies, and from our own de novo conceptualizations. Problematic character constructions inhibit the capacity of phylogenetic analyses to recover meaningful homology hypotheses and thus accurate clade structures. Upon a revision of two of the currently largest morphological datasets used to test squamate phylogeny, more than one‐third of the almost 1000 characters analysed were classified within at least one of our categories of “types” of characters that should be avoided in cladistic investigations. These characters were removed or recoded, and the data matrices re‐analysed, resulting in substantial changes in the sister group relationships for squamates, as compared to the original studies. Our results urge caution against certain types of character choices and constructions, also providing a methodological basis upon which problematic characters might be avoided.

A stem acrodontan lizard in the Cretaceous of Brazil revises early lizard evolution in Gondwana

Iguanians are one of the most diverse groups of extant lizards (>1,700 species) with acrodontan iguanians dominating in the Old World, and non-acrodontans in the New World. A new lizard species presented herein is the first acrodontan from South America, indicating acrodontans radiated throughout Gondwana much earlier than previously thought, and that some of the first South American lizards were more closely related to their counterparts in Africa and Asia than to the modern fauna of South America. This suggests both groups of iguanians achieved a worldwide distribution before the final breakup of Pangaea. At some point, non-acrodontans replaced acrodontans and became the only iguanians in the Americas, contrary to what happened on most of the Old World. This discovery also expands the diversity of Cretaceous lizards in South America, which with recent findings, suggests sphenodontians were not the dominant lepidosaurs in that continent as previously hypothesized.

A new Early Cretaceous lizard species from Brazil, and the phylogenetic position of the oldest known South American squamates

Squamates first appeared in South America during the Early Cretaceous. The oldest confirmed record is from the Lower Cretaceous Crato Formation of north-eastern Brazil. Unfortunately, our knowledge of squamate diversity in the Mesozoic of South America, and Gondwana as a whole, is extremely limited. This poses a barrier to our understanding of the origin and radiation of early squamates on this continent. Here we describe a new species – Calanguban alamoi gen. et sp. nov. – from the Crato Formation which shows morphological adaptations for a scansorial lifestyle. We also provide a phylogenetic analysis inclusive of this species and of the oldest known lizard species in South America, Tijubina pontei and Olindalacerta brasilensis. In an attempt to identify the phylogenetic position of these taxa we used two of the most recent morphological datasets for the phylogeny of the Squamata that contain the largest fossil taxon sampling available. Calanguban is a scleroglossan lizard, with scincomorph affinities, making it the oldest non-iguanian squamate from South America, and likely the oldest scincomorph lizard from that continent. Tijubina, and possibly Olindalacerta, fall within, or are closely allied to, polyglyphanodontids, a clade traditionally classified amongst teiioids with a wide distribution restricted to the northern hemisphere. Calanguban and the other Crato Formation species provide important clues about Gondwanan scincomorph evolution and also raise new questions on the origin of the first squamates in South America. http://zoobank.org/urn:lsid:zoobank.org:pub:CE86D7DB-DD4F-4DDE-A665-612442397CE1

Redescription of Tijubina pontei, an Early Cretaceous lizard (Reptilia; Squamata) from the Crato Formation of Brazil

The record of Gondwanan Mesozoic lizards is very poor. Among the few species described for this region there is Tijubina pontei, an Early Cretaceous lizard from the Crato Formation (late Aptian) of northeast Brazil. Its description is very brief and lacks most of its diagnostic characters and clear delimitation from other lizard species. Here, a full redescription of the holotype is provided. T. pontei is demonstrated to be a valid species and a new diagnosis is provided with reference to Olindalacerta brasiliensis, a contemporary species of the Crato Formation. It lacks the posteroventral and posterodorsal processes of the dentary; the tibial/fibular length equals the femoral length and its posterior dentary teeth are robust, cylindrically based, unsculptured and bear no cuspids. The systematic position of T. pontei still needs further clarification, but preliminary analyses indicate that it lies in a rather basal position among the Squamata, similarly to O. brasiliensis.

The oldest plesiosaur (Reptilia, Sauropterygia) from Antarctica

Antarctic plesiosaurs are known from the Upper Cretaceous López de Bertodano and Snow Hill Island formations (Campanian to upper Maastrichtian), which crop out within the James Ross Basin region of the Antarctic Peninsula. Here we describe the first plesiosaur fossils from the Lachman Crags Member of the Santa Marta Formation, north-western James Ross Island. This material constitutes the stratigraphically oldest plesiosaur occurrence presently known from Antarctica, extending the occurrence of plesiosaurians in this continent back to Santonian times (86.3–83.5 Mya). Furthermore, MN 7163-V represents the first plesiosaur from this region not referable to the Elasmosauridae nor Aristonectes, indicating a greater diversity of this group of aquatic reptiles in Antarctica than previously suspected.

Reacquisition of the lower temporal bar in sexually dimorphic fossil lizards provides a rare case of convergent evolution

Temporal fenestration has long been considered a key character to understand relationships amongst reptiles. In particular, the absence of the lower temporal bar (LTB) is considered one of the defining features of squamates (lizards and snakes). In a re-assessment of the borioteiioid lizard Polyglyphanodon sternbergi (Cretaceous, North America), we detected a heretofore unrecognized ontogenetic series, sexual dimorphism (a rare instance for Mesozoic reptiles), and a complete LTB, a feature only recently recognized for another borioteiioid, Tianyusaurus zhengi (Cretaceous, China). A new phylogenetic analysis (with updates on a quarter of the scorings for P. sternbergi) indicates not only that the LTB was reacquired in squamates, but it happened independently at least twice. An analysis of the functional significance of the LTB using proxies indicates that, unlike for T. zhengi, this structure had no apparent functional advantage in P. sternbergi, and it is better explained as the result of structural constraint release. The observed canalization against a LTB in squamates was broken at some point in the evolution of borioteiioids, whereas never re-occuring in other squamate lineages. This case of convergent evolution involves a mix of both adaptationist and structuralist causes, which is unusual for both living and extinct vertebrates.

The first iguanian lizard from the Mesozoic of Africa

The fossil record shows that iguanian lizards were widely distributed during the Late Cretaceous. However, the biogeographic history and early evolution of one of its most diverse and peculiar clades (acrodontans) remain poorly known. Here, we present the first Mesozoic acrodontan from Africa, which also represents the oldest iguanian lizard from that continent. The new taxon comes from the Kem Kem Beds in Morocco (Cenomanian, Late Cretaceous) and is based on a partial lower jaw. The new taxon presents a number of features that are found only among acrodontan lizards and shares greatest similarities with uromastycines, specifically. In a combined evidence phylogenetic dataset comprehensive of all major acrodontan lineages using multiple tree inference methods (traditional and implied weighting maximum-parsimony, and Bayesian inference), we found support for the placement of the new species within uromastycines, along with Gueragama sulamericana (Late Cretaceous of Brazil). The new fossil supports the previously hypothesized widespread geographical distribution of acrodontans in Gondwana during the Mesozoic. Additionally, it provides the first fossil evidence of uromastycines in the Cretaceous, and the ancestry of acrodontan iguanians in Africa.

Mosasauroid phylogeny under multiple phylogenetic methods provides new insights on the evolution of aquatic adaptations in the group

Mosasauroids were a successful lineage of squamate reptiles (lizards and snakes) that radiated during the Late Cretaceous (95–66 million years ago). They can be considered one of the few lineages in the evolutionary history of tetrapods to have acquired a fully aquatic lifestyle, similarly to whales, ichthyosaurs and plesiosaurs. Despite a long history of research on this group, their phylogenetic relationships have only been tested so far using traditional (unweighted) maximum parsimony. However, hypotheses of mosasauroid relationships and the recently proposed multiple origins of aquatically adapted pelvic and pedal features in this group can be more thoroughly tested by methods that take into account variation in branch lengths and evolutionary rates. In this study, we present the first mosasauroid phylogenetic analysis performed under different analytical methods, including maximum likelihood, Bayesian inference, and implied weighting maximum parsimony. The results indicate a lack of congruence in the topological position of halisaurines and Dallasaurus. Additionally, the genus Prognathodon is paraphyletic under all hypotheses. Interestingly, a number of traditional mosasauroid clades become weakly supported, or unresolved, under Bayesian analyses. The reduced resolutions in some consensus trees create ambiguities concerning the evolution of fully aquatic pelvic/pedal conditions under many analyses. However, when enough resolution was obtained, reversals of the pelvic/pedal conditions were favoured by parsimony and likelihood ancestral state reconstructions instead of independent origins of aquatic features in mosasauroids. It is concluded that most of the observed discrepancies among the results can be associated with different analytical procedures, but also due to limited postcranial data on halisaurines, yaguarasaurines and Dallasaurus.

Mesozoic Lizards from Brazil and Their Role in Early Squamate Evolution in South America

Abstract The diversity of extant squamates in South America is in deep contrast to the extremely scarce knowledge of squamates from that continent during the Mesozoic, particularly regarding terrestrial lizards. Here, we provide a review of the most recent advances in the knowledge of Cretaceous lizards from South America, focusing on named species (all from Brazil). These forms included scansorial, as well as cursorial taxa, likely displaying facultative bipedalism. In the case of Crato Formation specimens, only juveniles were reported so far, which raises questions about the role of taphonomic biases and community structure. Iguanians (acrodontans and non-acrodontans), as well as scincomorphs, are known since the Aptian/Albian. All iguanians had a broad Late Cretaceous distribution that, along with findings in the Early–Middle Jurassic of India, suggests an early radiation of the group before the final break up of Laurasia and Gondwana. Gondwanan regions may have played a fundamental role in the initial history of acrodontan iguanians despite the fact that, at least in South America, only non-acrodontans and scincomorphs are known to have passed through the Cretaceous–Paleogene boundary.

Mosasauroids from Gondwanan Continents

Abstract Herein, we present a revision of mosasauroid lizards (basal aigialosaurs + derived mosasaurids) from the Upper Cretaceous marine sediments associated with various Gondwanan landmasses. In stratigraphic terms, the Gondwanan fossil record of mosasaurs begins with basal mosasauroids from the carbonate platforms of the Middle East, in modern Israel. This record is followed by a dense Turonian record from Morocco and more rare specimens from the Turonian of Australia and Colombia. There is a substantial gap in the Coniacian and Santonian in Gondwana with only few known taxa, although the Campanian record from New Zealand is good (tylosaurines and mosasaurines), with additional rare specimens from Antarctica. Maastrichtian sediments from around the Gondwanan world are richly populated by a high diversity and density of all major clades of mosasaurid lizards. The mosasaurine Clidastes is currently not recognized from any Gondwanan marine deposit. The geographic and temporal patterns of distribution shown here are crucial for understanding the evolution of aquatic squamates not only in Gondwana but also globally.