Tyrannosauroidea

Hurum, J.H. and Sabath, K. 2003. Giant theropod dinosaurs from Asia and North America: Skulls of Tarbosaurus bataar and Tyrannosaurus rex compared. Acta Palaeontologica Polonica 48 (2): 161–190. The skull of a newly prepared Tarbosaurus bataar is described bone by bone and compared with a disarticulated skull of Tyrannosaurus rex. Both Tarbosaurus bataar and Tyrannosaurus rex skulls are deep in lateral view. In dorsal view, the skull of T. rex is extremely broad posteriorly but narrows towards the snout; in Ta. bataar the skull is narrower (especially in its ventral part: the premaxilla, maxilla, jugal, and the quadrate complex), and the expansion of the posterior half of the skull is less abrupt. The slender snout of Ta. bataar is reminiscent of more primitive North American tyrannosaurids. The most obvious difference between T. rex and Ta. bataar is the doming of the nasal in Ta. bataar which is high between the lacrimals and is less attached to the other bones of the skull, than in most tyrannosaurids. This is because of a shift in the handling of the crushing bite in Ta. bataar. We propose a paleogeographically based division of the Tyrannosaurinae into the Asiatic forms (Tarbosaurus and possibly Alioramus) and North American forms (Daspletosaurus and Tyranno− saurus). The division is supported by differences in anatomy of the two groups: in Asiatic forms the nasal is excluded from the major series of bones participating in deflecting the impact in the upper jaw and the dentary−angular interlocking makes a more rigid lower jaw.

Full citation: Alberta Palaeontological Society, 22nd Annual Meeting, Abstracts and short papers. Mount Royal University, Calgary, Alberta, March 17-18, 2018. Edited by H. Allen.

This is the story of Drumheller, Alberta, Canada man Maurice Stefanuk. He was a sonar operator on Flower-class corvettes in WWII, sending out the "ping" hunting for German U-Boats. He was very interested in fossils and made some major contributions, especially the two best known tyrannosaurid skeletons referable to Albertosaurus. He was also involved in lapidary including experimenting with ammonite shell producing something similar to what is known today as "ammolite". A fantastic love story is included.

A census of Hell Creek and Lance Formation dinosaur remains was conducted from April, 2017 through February of 2018. Online databases were reviewed and curators and collections managers interviewed in an effort to determine how much material had been collected over the past 130+ years of exploration. The results of this new census has led to numerous observations regarding the quantity, quality, and locations of the total collection, as well as ancillary data on the faunal diversity and density of Late Cretaceous dinosaur populations. By reviewing the available data, it was also possible to make general observations regarding the current state of certain exploration programs, the nature of collection bias present in those collections and the availability of today's online databases.

A total of 653 distinct, associated and/or articulated remains (skulls and partial skeletons) were located. Ceratopsid skulls and partial skeletons (mostly identified as Triceratops) were the most numerous, tallying over 335+ specimens. Hadrosaurids (Edmontosaurus) were second with at least 149 associated and/or articulated remains. Tyrannosaurids (Tyrannosaurus and Nanotyrannus) were third with a total of 71 associated and/or articulated specimens currently known to exist. Basal ornithopods (Thescelosaurus) were also well represented by at least 42 known associated and/or articulated remains. The remaining associated and/or articulated specimens, included pachycephalosaurids (18), ankylosaurids (6) nodosaurids (6), ornithomimids (13), oviraptorosaurids (9), dromaeosaurids (1) and troodontids (1).
Over 41,800 isolated bones and teeth, were also located. This number represents only a small fraction of the actual total collection as many of the museums and institutions surveyed were unable to provide complete numbers on isolated elements. Over 46% of these isolated bones and teeth were identified as hadrosauridae, usually identified as Edmontosaurus. Isolated elements identified as ceratopsids made up just over 21% of the total. These were generally identified as Triceratops. Isolated bones and teeth of tyrannosaurids were significantly less, at only 4.6%. The large difference between the associated and/or articulated remains and the isolated bones and teeth of tyrannosaurids (10.9% down to 4.6%) and ceratopsids (51.3% to 21.5%) is likely due to both a preservational and collection bias towards the larger, more likely to be fossilized, and more likely to be collected, Tyrannosaurus and Triceratops skeletons and skulls.

Even though small theropods accounted for less than 0.6% of the total recovered associated and/or articulated remains, their teeth and isolated elements were encountered quite frequently. Isolated bones and teeth of dromaeosaurids, troodontids and “unidentified small theropods” accounted for as much as 16% of the total number of isolated remains. This data suggests that there is a tremendous level of collection and preservational bias in the current Hell Creek and Lance sample set Actual small theropod diversity and populations in the Late Cretaceous were most likely much higher than previously considered.
It is highly likely that the fluvial and geochemical environment that dominated the Late Cretaceous of this region was simply too rough and tumble for bones of most genera under the 400 kg live weight

The Journal of Paleontological Sciences: JPS.C.2019.01 2
threshold to be preserved. Both preservational bias and collection bias appear to play significant roles in how we currently view the diversity of the Hell Creek and the Lance. This has directly influenced our perception of the end Cretaceous extinction event. It is entirely possible that many genera will never be known from more than fragmentary remains.

2003. Skull structure and evolution in tyrannosaurid dinosaurs. Acta Palaeonto− logica Polonica 48 (2): 227–234. Tyrannosauridae can be subdivided into two distinct subfamilies—the Albertosaurinae and the Tyrannosaurinae. Previ− ously recognized subdivisions Aublysodontinae and Shanshanosaurinae are rejected because they are based on insuffi− cient material and juvenile specimens. Our results are based upon a phylogenetic analysis using PAUP program (Swofford 1999) of 77 skull characters and seven genera (Albertosaurus, Alioramus, Daspletosaurus, Gorgosaurus, Nanotyrannus, Tarbosaurus, and Tyrannosaurus); with Allosaurus as outgroup. Of the 77 characters used, more than half were parsimony informative. A single most parsimonious tree was obtained with the Tree Length being 88. The analysis of cranial characters and comparison of postcranial features reveal that Tarbosaurus bataar is not the sister taxon of Tyrannosaurus rex (contra Holtz 2001). Their similarities are partially due to the fact that both are extremely large ani− mals. Thus, Tarbosaurus should be considered a genus distinct from Tyrannosaurus.

Three nearly complete, isolated vertebrae, and a right humerus of a sub-adult hadrosaurine (Ornithopoda: Hadrosaurinae), all from separate individuals and from the Late Cretaceous (late Campanian) Hunter Wash local fauna (Fruitland Formation [Fossil Forest Member] and Kirtland Formation [Hunter Wash Member]), San Juan Basin, New Mexico, bear distinctive bite marks. These bite marks vary in size and shape, suggesting that different species of theropods, or possibly different ontogenetic individuals of a single species, were feeding on the carcasses pertaining to these individual elements. The isolated vertebrae suggest post-mortem bites, probably from scavenging behavior, whereas the bite marks on the humerus may have been inflicted during predation. Based on the bite mark traces, it appears that all bite marks were made by tyrannosauroids of different ontogenetic stages and/or different species.

La evolución de los tiranosauroideos, uno de los grupos de dinosaurios carnívoros más ubicuo del Mesozoico, se produjo a lo largo de 100 millones de años. Tuvieron una amplia distribución geográfica y algunos de sus representantes están entre los carnívoros terrestres más grandes que han existido. En este trabajo abordamos cuestiones sobre la paleobiogeografía del grupo aplicando un modelo de reconstrucción de rangos geográficos ancestrales basado en máxima probabilidad. Nuestro estudio apoya un origen ...

Coprolites from the Upper Cretaceous Fruitland, Kirtland and Ojo Alamo formations in the vertebrate paleontology collection of the State Museum of Pennsylvania consist of different forms that are identified as morphotypes A-G. These coprolites are attributed to carnivorous vertebrates (fishes, turtles and crocodylians). At least four unique Upper Cretaceous coprolite morphotypes (B, D, F and G) are recognized. Four different surface textures are also recognized (smooth, slightly blistered, wrinkled and striated), but only partially coincide with the morphotypes. Bone inclusions are common in about half of the coprolites, and one contains the ?astragalus and ?calcaneum of an anuran, the first record of an anuran in a Late Cretaceous coprolite. A large, irregular bony mass containing large and small fragments of a ?scapula blade, ?vertebral centra and partially digested bone is identified as a probable tyrannosauroid coprolite. The large ?scapula blade fragment appears to be from a sub-adult hadrosaurid. This specimen potentially represents the third record of a carnosaur coprolite, and the first from the United States and New Mexico.

Abstract The Cabullona Basin in the state of Sonora, Mexico is becoming recognized due to its diversity of southern Laramidian continental vertebrates, especially dinosaurs. In this study we describe and analyze three theropod teeth (ERNO specimens) that were found isolated and surface collected in the Corral de Enmedio Formation (Cabullona Group, Upper Cretaceous). The three specimens possess similar morphological characteristics that match the ones present in Late Cretaceous Laramidian tyrannosaurids, so they were referred to the Tyrannosauridae, probably belonging to a new unknown taxon. The implementation of statistical and cladistic analyses corroborated their taxonomical assignment. ERNO specimens correspond to the first record of tyrannosaurid dinosaurs in the basal Corral de Enmedio Formation, extending the stratigraphic distribution of these dinosaurs in the Cabullona Basin. Although tyrannosaurids have been previously described in the Cabullona Basin, the ERNO specimens of the Corral de Enmedio Formation seem to be different, because they possess more labiolingually compressed teeth. This new evidence could indicate a higher taxonomic diversity of the tyrannosaurid theropods that were present in the Cabullona Basin, adding more information to the Tyrannosauridae diversification on one of the most southern Laramidian regions during the Late Cretaceous.

This study provides a detailed osteological description of an isolated proximal caudal centrum and two nearly complete isolated metatarsals II and IV of the left foot of a gracile theropod dinosaur from the Lower Campanian of the Merchantville Formation in northern Delaware, USA. The caudal centrum and the metatarsals are referred to Tyrannosauroidea. The centrum is not well preserved, and thus not diagnostic; however, both metatarsals are diagnostic. The referral to Tyrannosauroidea is supported by several morphological features, including extensive surfaces on metatarsals II and IV for the articulation with metatarsal III, and a characteristic low, slightly convex muscle scar on metatarsal IV developed as a thin low ridge located on the posterior surface between the M. gastrocnemius pars lateralis insertion scar and the metatarsal III articular surface. This ridge has been previously interpreted as the plantar ridge, which is present in some derived Late Campanian tyrannosauroid taxa. Additionally, metatarsal IV has a deep medial notch for the accommodation of an “L”– shaped proximal articulation of metatarsal III, and a “U”– shaped proximal articular end. The Merchantville Formation tyrannosauroid exhibits arctometatarsalian metatarsals, as do tyrannosaurids. The Merchantville Formation tyrannosauroid is differentiated from other known basal and derived tyrannosaurids by having a characteristically shaped proximal articular surface of metatarsal II in which the proximal and posterior ends lie on the long axis of the proximal articular surface. However, the posterior proximal articular surface of metatarsal II is not as strongly angled laterally as in more derived tyrannosauroids. The Merchantville Formation tyrannosauroid adds to the record of Appalachian tyrannosauroid, evolution and paleostratigraphic position, and provides new morphological information about the metatarsal anatomy of these iconic theropods.

Aublysodon is an enigmatic theropod known from distinctive small D-shaped unserrated premaxillary teeth. The anterior edge of the tooth is round while the posterior end is nearly flat with carina on the posterior edges. The type tooth lacks serrations on the carinae, but several other D-shaped teeth bear serrations and have on occasion been attributed to both Aublysodon and Tyrannosauridae. The validity of Aublysodon is questionable, and teeth referred to this genus are considered to be juveniles of known tyrannosaurids. A new type of D-shaped tooth has been found from Baja California, Mexico. The teeth are similar to Aublysodon in overall morphology, but differ in that the anterior crown surfaces is flat and the carinae are serrated. The type Aublysodon lacks serrations, but other specimens originally believed to have lacked serrations do indeed have serrations. Teeth referred to Aublysodon are either juveniles of known tyrannosaurids or a nomen dubium.