Paul Sereno

Diverse crocodyliforms have been discovered in recent years in Cretaceous rocks on southern landmasses formerly composing Gondwana. We report here on six species from the Sahara with an array of trophic adaptations that signifi cantly deepen our current understanding of African crocodyliform diversity during the Cretaceous period. We describe two of these species (Anatosuchus minor, Araripesuchus wegeneri) from nearly complete skulls and partial articulated skeletons from the Lower Cretaceous Elrhaz Formation (Aptian-Albian) of Niger. Th e remaining four species (Araripesuchus rattoides sp. n., Kaprosuchus saharicus gen. n. sp. n., Laganosuchus thaumastos gen. n. sp. n., Laganosuchus maghrebensis gen. n. sp. n.) come from contemporaneous Upper Cretaceous formations (Cenomanian) in Niger and Morocco.

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... The Anatomical Record, 279: 676–684. Calvo, JO, Rubilar-Rogers, D., and Moreno, K. 2004. A new Abelisauridae (Dinosauria: Theropoda) from northwest Patagonia. Ameghiniana, 41: 555–563. ... Chure, DJ 2000. On the orbit of theropod dinosaurs. Gaia, 15: 233–240. ...

Fluorescence using ultraviolet (UV) light has seen increased use as a tool in paleontology over the last decade. Laser-stimulated fluorescence (LSF) is a next generation technique that is emerging as a way to fluoresce paleontological specimens that remain dark under typical UV. A laser's ability to concentrate very high flux rates both at the macroscopic and microscopic levels results in specimens fluorescing in ways a standard UV bulb cannot induce. Presented here are five paleontological case histories that illustrate the technique across a broad range of specimens and scales. Novel uses such as back-lighting opaque specimens to reveal detail and detection of specimens completely obscured by matrix are highlighted in these examples. The recent cost reductions in medium-power short wavelength lasers and use of standard photographic filters has now made this technique widely accessible to researchers. This technology has the potential to automate multiple aspects of paleontolog...

"An articulated skull and postcranial skeleton of a pelomedusoid turtle, Laganemys tenerensis gen. et sp. nov., is described from the Lower Cretaceous (Aptian–Albian) Elrhaz Formation in Niger. Laganemys has a proportionately long skull, which increases in depth anteriorly, from the occiput to the snout. The thin flat carapace and plastron are covered with fine sulcus-and-ridge texture. The carapace has a deep nuchal embayment anteriorly, a small mesoplastron laterally, and three median fenestrae. The cervical series is nearly as long as the carapace with specialized joints to enhance lateral flexion between cervicals 2 and 3 and cervicals 6 and 7. The relatively long tail is composed of at least 26 vertebrae. Forelimbs and hind limbs have long and relatively straight unguals. Discovered in a fluvial setting, Laganemys would have been an adept long-necked aquatic predator in still waters. A suite of derived features unites Laganemys tenerensis with Araripemys barretoi, a pelomedusoid from northeastern Brazil of similar form, habits and geologic age. These genera provide additional evidence of faunal exchange between South America and Africa in the mid Cretaceous (ca. 110 Mya) prior to the advent of deep waters in the central Atlantic Ocean."

Heterodontosaurids comprise an important early radiation of small-bodied herbivores that persisted for approximately 100 My from Late Triassic to Early Cretaceous time. Review of available fossils unequivocally establishes Echinodon as a very small-bodied, late-surviving northern heterodontosaurid similar to the other northern genera Fruitadens and Tianyulong. Tianyulong from northern China has unusual skeletal proportions, including a relatively large skull, short forelimb, and long manual digit II. The southern African heterodontosaurid genus Lycorhinus is established as valid, and a new taxon from the same formation is named Pegomastax africanusgen. n., sp. n. Tooth replacement and tooth-to-tooth wear is more common than previously thought among heterodontosaurids, and in Heterodontosaurus the angle of tooth-to-tooth shear is shown to increase markedly during maturation. Long-axis rotation of the lower jaw during occlusion is identified here as the most likely functional mechanism underlying marked tooth wear in mature specimens of Heterodontosaurus. Extensive tooth wear and other evidence suggests that all heterodontosaurids were predominantly or exclusively herbivores. Basal genera such as Echinodon, Fruitadens and Tianyulong with primitive, subtriangular crowns currently are known only from northern landmasses. All other genera except the enigmatic Pisanosaurus have deeper crown proportions and currently are known only from southern landmasses.

Phylogenetic taxonomy, like modern Linnean taxonomy, was modeled on a phylogenetic tree rather than a cladogram and, like its predecessor, perpetuates the use of morphology as a means of recognizing clades. Both practices have generated confusion in graphical representation, operational terminology, and definitional rationale in phylogenetic taxonomy, the history of which is traced. The following points are made: (1) cladograms, rather than trees or hybrid cladogram-trees, provide the framework for the simplest graphical depiction of phylogenetic definitions; (2) a complete notational scheme for phylogenetic definitions is presented that distinguishes symbolic notation from shorthand and longhand versions; (3) phylogenetic definitions are composed of three components (paradigm, specifier, qualifier) arranged in two fundamental patterns-node and stem; (4) apomorphies do not constitute a fundamental definitional pattern but rather serve to qualify a stem-based definition (as do time and geographic range); (5) formulation of phylogenetic definitions involves three heuristic criteria (stability, simplicity, prior use); (6) reasoned definitional revision is encouraged and better defined (textual substitution, first-and second-order revision); and (7) a database, TaxonSearch, allows rapid recall of taxonomic and definitional information.

A major question in Mesozoic biogeography is how the land-based dinosaurian radiation responded to fragmentation of Pangaea. A rich fossil record has been uncovered on northern continents that spans the Cretaceous, when continental isolation reached its peak. In contrast, dinosaur remains on southern continents are scarce. The discovery of dinosaurian skeletons from Lower Cretaceous beds in the southern Sahara shows that several lineages of tetanuran theropods and broad-toothed sauropods had a cosmopolitan distribution across Pangaea before the onset of continental fragmentation. The distinct dinosaurian faunas of Africa, South America, and Asiamerica arose during the Cretaceous by differential survival of once widespread lineages on land masses that were becoming increasingly isolated from one another.

We describe a new species of psittacosaur, Psittacosaurus gobiensis, from the Lower Cretaceous of Inner Mongolia and outline a hypothesis of chewing function in psittacosaurs that in many respects parallels that in psittaciform birds. Cranial features that accommodate increased bite force in psittacosaurs include an akinetic skull (both cranium and lower jaws) and differentiation of adductor muscle attachments comparable to that in psittaciform birds. These and other features, along with the presence of numerous large gastroliths, suggest that psittacosaurs may have had a high-fibre, nucivorous (nut-eating) diet. Psittacosaurs, alone among ornithischians, generate oblique wear facets from tooth-to-tooth occlusion without kinesis in either the upper or lower jaws. This is accomplished with a novel isognathous jaw mechanism that combines aspects of arcilineal (vertical) and propalinal (horizontal) jaw movement. Here termed clinolineal (inclined) jaw movement, the mechanism uses posteriorly divergent tooth rows, rather than kinesis, to gain the added width for oblique occlusion. As the lower tooth rows are drawn posterodorsally into occlusion, the increasing width between the upper tooth rows accommodates oblique shear. With this jaw mechanism, psittacosaurs were able to maintain oblique shearing occlusion in an akinetic skull designed to resist high bite forces.

Abelisauroid predators have been recorded almost exclusively from South America, India and Madagascar, a distribution thought to document persistent land connections exclusive of Africa. Here, we report fossils from three stratigraphic levels in the Cretaceous of Niger that provide definitive evidence that abelisauroid dinosaurs and their immediate antecedents were also present on Africa. The fossils include an immediate abelisauroid antecedent of Early Cretaceous age (ca. 130-110 Myr ago), early members of the two abelisauroid subgroups (Noasauridae, Abelisauridae) of Mid-Cretaceous age (ca. 110 Myr ago) and a hornless abelisaurid skull of early Late Cretaceous age (ca. 95 Myr ago). Together, these fossils fill in the early history of the abelisauroid radiation and provide key evidence for continued faunal exchange among Gondwanan landmasses until the end of the Early Cretaceous (ca. 100 Myr ago).

... Paul C. Sereno * , Catherine A. Forster * , Raymond R. Rogers † & Alfredo M. Monetta ‡. ... | Article |. 18. Hunt, AP in Dawn of the Age of Dinosaurs in the American Southwest (eds Lucas, SG & Hunt, AP) 355−358 (New Mexico Museum of Natural History, Albuquerque, 1989). 19. ...

A Cretaceous eucosmodont multituberculate mammal skeleton has been found in Mongolia with all of the bony elements of the shoulder girdle in place. This specimen demonstrates a different forelimb stance from that recently hypothesized for another Cretaceous ...

... In fact, measured just above the fibular flange, the distal end of the tibia is signifi-cantly deeper than broad. This proportion must be autapomorphic for P. mertii, since the depth of the distal end never exceeds the width in the herrerasaurids Herrerasaurus and Staurikosaurus. ...

... 4, 1993 FIGURE 6. Stereopair of the left elbow joint of Herrerasaurus ìschigualastensis (PVSJ 373) in ... also with the margins of distal carpáis 1 and 2. The radiale has a tabular shape. The concave articular surface for the radius is oval in proximal view with angular medial and ...