Search

Currently known from the early Campanian to late Maastrichtian, Prognathodon constitutes a group of mosasaurine mosasaurs that typically possessed massive jaws. Only four articulated skulls are known to date and the information concerning their postcrania remains minimal. Moreover, the early to middle Campanian specimens of the taxon are extremely rare and fragmentary. Two new specimens of Prognathodon overtoni from the early late Campanian (ca. 74.5 Ma) Bearpaw Formation exposed near Welling, southern Alberta, Canada, provide the first fully articulated skeletons of the genus. Detailed morphological assessment of these and pre-existing specimens indicates that many cranial characters are shared between P. overtoni and the generic type P. solvayi from the early Maastrichtian, including (1) short premaxillary-maxillary suture; (2) short triangular frontal with marked anterior constriction; and (3) distinct, blind-ended median opening on medullary floor of basioccipital. These are interpreted as ge...

—Ichthyosaurus conybeari is a rare species, previously known only from an incomplete holotype and one referred specimen, both from the Lyme Regis area of the west Dorset coast, U. K. A newly recognized, nearly complete specimen (NMW 93.5G.2) is the first occurrence of the species in Somerset, U. K. A revised diagnosis recognizes new morphological characters that distinguish the species: slender maxilla with a long, delicate premaxillary process; narrow postorbital; humerus with an anteriorly offset dorsal process that has a well-defined lip extending slightly into the shaft; fibula that is much larger dorsoventrally and mediodistally than tibia; and wide rectangular ischium that is much shorter than the pubis and femur. Notching of anterior fin elements in the forefin had been used as a diagnostic character, but a review of notching within Ichthyosaurus suggests that it has little taxonomic utility. Another specimen (NHMUK R15907), herein referred to the species, extends the range of I. conybeari ...

We describe a new species of Lower Jurassic (Hettangian/Sinemurian–Pliensbachian) ichthyosaur, Ichthyosaurus anningae, sp. nov., from west Dorset, England, U.K. The holotype of I. anningae (DONMG:1983.98), at least a subadult, is from the lower Pliensbachian Stonebarrow Marl Member (Charmouth Mudstone Formation). It is the most complete ichthyosaur known from this time interval worldwide. The species is assigned to Ichthyosaurus on the basis of humerus, forefin, and pectoral girdle morphologies. Diagnostic features of the species include a short, robust humerus with prominent processes; a femur in which the proximal width is almost as large as the distal width; and a very small femur relative to the humerus (humerus/femur ratio >1.7). Four other specimens, at least three of which are juveniles, are referred to this species. The new species may display sexual dimorphism in humeral morphology, but this cannot be confirmed due to a lack of stratigraphic information. With the recognition of I. anninga...

The large reptilian marine predators of the Mesozoic preyed upon pelagic animals such as bony fish, sharks, soft cephalopods, belemnoids, ammonoids, and even each other. All had undifferentiated conical teeth of one of several forms ranging from a blunt, bulbous shape to a slender, sharply pointed cone, to a robust, slightly compressed cone with two distinct cutting edges. Tooth form, along with tooth wear and occasionally preserved stomach contents, suggests the preferred prey of each species. Seven somewhat overlapping predator types, or guilds, can be defined on the basis of tooth form and prey preference. Members of each guild have tooth morphologies which fall within a defined range, and thus they probably shared the same preferred prey. The guilds present in six well-preserved faunas of the Jurassic and Cretaceous illustrate the structure of and changes in the large marine predator adaptive zone. Six guilds co-existed for most of the Jurassic. Although the composition of some of the guilds ...