Ángela Delgado Buscalioni

A NEW SPECIES OF ARARIPESUCHUS (CROCODYLOMORPHA, MESOEUCROCODYLIA) FROM THE LOWER CRETACEOUS OF PATAGONIA (ARGENTINA)

Abstract A new species of the genus Araripesuchus from the Albian–Cenomanian locality of the El Chocón (Neuquén Province, Argentina) is described. The diagnosis of the genus is reviewed and its phylogenetic placement within Crocodylomorpha discussed. Araripesuchus is proposed here as being the sister taxon of Neosuchia, corroborating previous phylogenetic analysis. The new species, Araripesuchus patagonicus, differs from the type species, A. gomesii in the relationships of the prefronto-nasal and lachrymo-nasal sutures, the dermal placement of the postorbital bar on the medial side of the jugal, and the greater extension of the squamosals in the skull dorsum. The African species, “Araripesuchus” wegeneri, does not share the diagnostic traits of the genus, and its reassignment to a new genus needs to be considered. The phylogenetic context of Araripesuchus and “A.” wegeneri permits a reanalysis of the role played by their amphiatlantic distribution in the Aptian-Albian. “Araripesuchus” wegeneri and the South American forms might share a pre-Aptian common ancestor, and have been already differentiated and isolated in the African and South American continents by the time of the Aptian–Albian.

A revision of the crocodyliform Allodaposuchus precedens from the Upper Cretaceous of the Hateg Basin, Romania. Its relevance in the phylogeny of Eusuchia

Abstract This paper describes the skull of Allodaposuchus precedens Nopcsa, 1928 and provides the first complete diagnosis of the species. The description of the holotype, which comes from the Upper Cretaceous deposits of Valioara in the Hateg Basin of Romania (Late Maastrichtian), is included with those of other undescribed specimens from the uppermost Cretaceous of Spain and southern France. All the specimens preserve the same anatomical region as the holotype and provide new relevant information on the genus Allodaposuchus and its phylogenetic position. The phylogenetic context of A. precedens is discussed in the context of a recent cladistic analysis of Eusuchia and its crown-group Crocodylia. Allodaposuchus is unambiguously the sister taxon of the crown-group Crocodylia, sharing with this clade the absence of a lingual to maxillary occlusion of the dentary teeth, and the extension of the ectopterygoid that does not reach the posterior tip of the lateral pterygoid flange, among other characters. The phylogenetic analysis also raises the problem of the ambiguous definition of Eusuchia, since the characters traditionally used in its diagnosis are multiply derived. Allodaposuchus is an outstanding crocodyliform providing new anatomical evidence concerning the stem-group of Crocodylia, and filling the gap between the Early Cretaceous (Barremian) Hylaeochampsa and the earliest common ancestor of Crocodylia.

An Early Cretaceous faunal and floral continental assemblage: Las Hoyas fossil site (Cuenca, Spain)

Abstract The fossiliferous beds of Las Hoyas (province ofCuenca, Spain) are composed of limestones (probably Late Hauterivian). The main fossiliferous facies consists of laminated limestone from a lake-basin plain with bottom waters perennially anoxic. The floral and faunal assemblage is similar to that of Montsech (prov. of Lerida, Spain), with divergences especially in the insects and some tetrapods. Bottom-dwelling invertebrates are scarce. Most of invertebrates are arthropods: three crustaceans and a relatively diversified entomofauna. The fishes are the main component of the vertebrate fauna both in number of individuals and diversity (13 different taxa). Among tetrapods the most abundant is a new genus of Caudata. Reptiles are represented by a chelonian, a little lizard and an atoposaurid crocodile. Finally, a new bird is reported from Las Hoyas, with an intermediate phylogenetic position between Archaeopteryx and Ornithurae.

The Gavialis--Tomistoma debate: the contribution of skull ontogenetic allometry and growth trajectories to the study of crocodylian relationships

SUMMARY The phylogenetic placement of Tomistoma and Gavialis crocodiles depends largely upon whether molecular or morphological data are utilized. Molecular analyses consider them as sister taxa, whereas morphological/paleontological analyses set Gavialis apart from Tomistoma and other crocodylian species. Here skull allometric trajectories of Tomistoma and Gavialis were contrasted with those of two longirostral crocodylian taxa, Crocodylus acutus and Mecistops cataphractus, to examine similarities in growth trajectories in light of this phylogenetic controversy. Entire skull shape and its two main modules, rostrum and postrostrum, were analyzed separately. We tested differences for both multivariate angles between trajectories and for shape differences at early and late stages of development. Based on a multivariate regression of shape data and size, Tomistoma seems to possess a peculiar rate of growth in comparison to the remaining taxa. However, its morphology at both juvenile and adult sizes is always closer to those of Brevirostres crocodylians, for the entire head shape, as well as the shape of the postrostrum and rostrum. By contrast, the allometric trajectory of Gavialis always begins and ends in a unique region of the multidimensional morphospace. These findings concur with a morphological hypothesis that places Gavialis separate from Brevirostres, and Tomistoma closer to other crocodylids, and provides an additional, and independent, data set to inform on this ongoing phylogenetic discussion.

Reinterpretation and new denominationof Atacisaurus crassiproratus (Middle Eocene; Issel, France) as cf. Iberosuchus (Crocodylomorpha, Metasuchia)

Abstract The holotype of Atacisaurus crassiproratus Astre , 1931 (Middle Eocene; Issel, France) is herein reinterpreted and attributed to cf. Iberosuchus. The holotype of A. crassiproratus consists of a fragment of a mandible that Astre (1931) assigned to an eusuchian crocodile. However, the combination of characters that we have recognized in this mandible allows to consider it as a member of the Metasuchia clade (sensu Benton & Clark 1988 ). Furthermore, the specimen from Issel shows a similar morphology and the same combination of character states than those of several specimens from the middle Eocene site of Caenes (Duero basin, Salamanca province, Spain). We consider that both the Issel and Caenes mandibles belong to the same taxon. The mandibles of all these specimens, attributed to cf. Iberosuchus, share with other metasuchians the following combination of apomorphic traits: a dorsal prolongation of the dentary ascending behind the tooth row; the presence of a lateral depression on the dentary; robust splenials; the presence of a big slot-like foramen intramandibularis oralis;; and an anteroposteriorly elongated glenoid fossa of the articular. These specimens are also compared with the Eocene African species Eremosuchus elkoholicus Buffetaut , 1989 . The phylogenetic relationships, based on mandibular characters, of cf. Iberosuchus with other taxa previously associated to this genus, such as the Sebecosuchia Simpson 1937 (sensu Gasparini et al. 1991 ) and the Trematochampsidae Buffetaut, 1974 (sensu Buffetaut, 1986 , Buffetaut, 1988 , Buffetaut, 1989 ), as well as with other members of the Metasuchia and Neosuchia clade, are discussed.

Phylogenetic relationships of the Atoposauridae (archosauria, crocodylomorpha)

A systematic revision of the family Atoposauridae is presented, interpreting and reviewing their relationships. The seventy‐one characters have been divided into cranial, postcranial and metric which have been used in three separate cladistic analyses in order to discuss their concordance. Polarities, in each case, have been deduced from distinct outgroups. We have used a PHYLIP program (version 2.9). There are five valid taxa of Atoposauridae: Alligatorellus beaumonti (rejecting the two subspecific taxa) Alligatorium meyeri, Theriosuchus pusillus. Alligatorium depereti (which is transferred to a new genus Montsecosuchus) and Aloposaurus (discussed as a nomen dubium). The three cladograms are not fully concordant. The relative level of derivation in postcranial and cranial characters suggests congruence. The metric traits seem to retain, in general, a primitive condition. The final proposed cladogram clusters Alligatorium + Alligatorellus as the sister group of Montsecosuchus + Theriosuchus.

A holistic approach to the palaeoecology of Las Hoyas Konservat-Lagerstätte (La Huérguina Formation, Lower Cretaceous, Iberian Ranges, Spain)

The Las Hoyas fossil site (Lower Cretaceous, Iberian Ranges, Spain) is a classic lacustrine Fossil-Lagerstatte that exemplifies the features predicted by the original concept of Konservat-Lagerstatten in relation to the quantity of remains, quality of preservation, completeness, and preservation by a combination of obrution, stagnation and, in this case, mainly bacterial sealing. Fossils are preserved in rhythmically laminated limestones deposited in a environment that underwent strong,climatically driven cyclical oscillations in water level within the framework of a seasonal, subtropical, regional-scale wetland. Extensive systematic layer-bylayer excavation and geological research have resulted in a comprehensive understanding of the stratigraphy and sedimentology of the locality and its regional palaeogeography. Two approaches have allowed the palaeoecology of the fossil association to be reconstructed. Firstly, autoecological reconstructions of the fossil groups are supplemented by palaeoenvironmental reconstructions based on the sedimentology. This considers taphonomic features and the ecological structure of the whole association, including vegetation and animals. The organization of the ecosystem resembles that of extant lentic ecosystems. It is dominated by obligate aquatic and amphibious organisms; facultative terrestrial organisms are scarce. Several lines of evidence from flora and fauna indicate strong seasonality and water stress. The second approach is dynamic and aims to unravel the information transferred to the fossil record about ecological dynamics and evolution by combining stratigraphical and palaeontological information and integrating this in a spatial and temporal framework. This analysis illustrates that Las Hoyas has a significant facies bias, reflecting alternating wet and dry climatically controlled periods. The biotic response these wet and dry cycles produced a coupling of taphonomic and sedimentary processes that resulted in the characteristic cyclical arrangement of the stratigraphic and palaeontological record. Las Hoyas therefore represents a subtropical seasonal wetland impacted by cyclicity and ecological stress. This stress impeded shortterm ecological evolution and resulted in a stable ecosystem that lasted for thousands of years. The results of this study also have implications for the concept of Konservat-Lagerstatten and its limitations. Whereas the former approach considers Las Hoyas as a canon of minimally biased information (as it is a Konservat-Lagerstatte), the latter approach reveals the biased characteristics of the association. The study illustrates that although all Konservat-Lagerstatten share similar preservational mechanisms, the paleoecological information that contain may differ. [RESUMEN] El yacimiento de Las Hoyas (Cretacico Inferior, Cordillera Iberica, Espana) es un clasico Fossil-Lagerstatte lacustre que encaja perfectamente con los rasgos que predice el concepto de Konservat-Lagerstatte en lo relativo a la abundancia de restos, calidad de conservacion, completitud y genesis del deposito debido a la combinacion de factores relacionados con el enterramiento rapido, el estancamiento y, en el caso particular de Las Hoyas, elsellado bacteriano. Los fosiles se conservan en calizas finamente laminadas que fueron depositadas en un ambiente que estuvo sujeto a fuertes oscilaciones ciclicas en el nivel de agua, climaticamente reguladas, en el marco de un humedal estacional y subtropical de escala regional. Las profusas excavaciones sistematicas realizadas capa a capa, y la investigacion geologica han dado lugar a un profundo conocimiento de la estratigrafia y sedimentologia de la localidad y de su paleogeografia regional. Una doble aproximacion a la interpretacion de las asociaciones fosiles ha permitido la reconstruccion paleoecologica de la localidad. La primera parte de las reconstrucciones autoecologicas de los grupos fosiles retroalimentadas por la reconstruccion paleoambiental basada en la sedimentologia. En esta aproximacion se consideran las caracteristicas tafonomicas y la estructura ecologica de la asociacion completa, incluyendo la ecologia vegetal y animal. La organizacion del ecosistema sigue un patron semejante al de los ecosistemas lenticos actuales. Este ecosistema se caracteriza por la dominancia de organismos acuaticos obligados y de categorias anfibias y por la escasez de formas facultativas terrestres. Hay evidencias diversas, en la flora y en la fauna, de estrategias ecologicas vinculadas a la fuerte estacionalidad y al estres hidrico. La segunda aproximacion es dinamica, y pretende desvelar la informacion transferida al registro fosil en cuanto a la dinamica ecologica y su evolucion mediante la combinacion de informacion proporcionada por datos estratigraficos y paleontologicos, de modo que los datos son interpretados en terminos de su marco y significado espacial y temporal. Este analisis muestra que Las Hoyas tiene un sesgo significativo de facies (facies bias), reflejando la alternancia de periodos humedos y aridos controlados climaticamente. La respuesta biotica a estos ciclos humedos y aridos produjo un acoplamiento entre los procesos tafonomicos y sedimentarios que da lugar a una estructura ciclica del registro estratigrafico y paleontologico de Las Hoyas. Por consiguiente, Las Hoyas representa un humedal subtropical estacional regido por la ciclicidad y por el estres ecologico. Dicho estres impide una evolucion ecologica a corta escala dando lugar a un ecosistema estable que debio durar miles de anos. El resultado de este estudio tiene algunas implicaciones en el concepto de Konservat-Lagerstatten y en sus limitaciones. Mientras que bajo la primera aproximacion Las Hoyas se consideraria canon de informacion con un sesgo minimo, puesto que es un deposito de conservacion excepcional, la segunda aproximacion pone de manifiesto el sesgo presente en la asociacion. Este estudio ilustra que aunque todos los Konservat-Lagerstatten comparten mecanismos de conservacion similares, la informacion paleoecologica que contienen difiere entre ellos.

A NEW SPECIES OF DORATODON (CROCODYLIFORMES: ZIPHOSUCHIA) FROM THE LATE CRETACEOUS OF SPAIN

Abstract A new species of a ziphodont crocodyliform is described on the basis of newly-discovered material from the Late Cretaceous (Campanian) Sierra Perenchiza Formation of Valencia, Spain. It is referred to the genus Doratodon as D. ibericus sp. nov. To date, Doratodon (type-species D. carcharidens) was only known by fragmentary cranial remains from the Campanian of Muthmannsdorf (Austria). This genus was previously regarded either as a goniopholid or as a hsisosuchid within the Mesoeucrocodylia, but a phylogenetic analysis suggests that Doratodon is a member of Ziphosuchia, placing it as the sister taxon of Sebecosuchia. Doratodon shares with Sebecosuchia (including Bergisuchus) features concerning the shape and implantation of teeth (margins of tooth crowns with denticulate carinae; tip of tooth crowns caudally curved; tooth implantation in isolated alveoli). Its inclusion in Ziphosuchia is based also on mandibular traits (splenials broad and robust behind symphysis, sculpturing of lateral surface of dentary based on development of longitudinal depression). The absence of the external mandibular fenestra is an autopomorphy of Doratodon in the context of Ziphosuchia. Doratodon is characterized by: short and narrow rostrum with reduced dentition (11 to 13 dentary teeth); dorsal profile of lower jaw showing two vertical waves. The most distinctive characteristic of the new species relative to D. carcharidens is the heterodonty in size of teeth, especially in the caudal part of the dental series. From a palaeobiogeographical point of view, Doratodon represents the first occurrence of a sebecosuchian-like crocodyliform in the Late Cretaceous of Europe.

New crocodiles (Eusuchia: Alligatoroidea) from the Upper Cretaceous of southern Europe

The Upper Cretaceous sites of Lano and Quintanilla del Coco in northern Spain have yielded significant crocodilian remains, allowing a more precise interpretation of the fragmentary record of southwestern Europe. Two new genera, Musturzabalsuchus and Acynodon, have been recognized. Both taxa were extinct at the end of the Cretaceous. Their relationships with the alligatoroidean Eusuchia suggest a close relationship with Paleolaurasian groups. Musturzabalsuchus might be regarded as an endemic european taxa, the oldest known member of the basal Alligatoroidea. Acynodon is the only non-North American taxon that is related to the short snouted Upper Cretaceous alligatorids.

Theoretical morphology of the Archosaur (Reptilia: Diapsida) pelvic girdle

Abstract Theoretical models of skeletal structures provide suitable frameworks to assess macroevolutionary patterns of form change. We discuss three theoretical approaches to account for morphological patterns of the pelvic girdle in archosaurs. Every approach targets a different level of organization within the concept of morphospace. First, we build a morphocline by applying a mathematical transformation to the outline of the hip of the theropod dinosaur Deinonychus antirrhopus, in order to look at theoretical paths of evolutionary change based on changes of proportion. Second, we analyze the variability of a sample of 86 hips within a theoretical construction that incorporates information about the spatial orientation of the three paired bones that build this skeletal compound. Finally, we look at boundary patterns within these hips as a basis for generating a formalism based on graph theory. Insights about the evolution and development of the archosaur triradiate pelvis and its morphological trends are suggested in the light of each theoretical approach, with a special focus on the convergent evolution of a retroverted pubis in ornithischians and birds.