Sebastian Dalman

Montana State University | MSU · Department of Earth Sciences

Tyrannosaurid dinosaurs dominated as predators in the Late Cretaceous of Laurasia, culminating in the evolution of the giant Tyrannosaurus rex, both the last and largest tyrannosaurid. Where and when Tyrannosaurini (T. rex and kin) originated remains unclear. Competing hypotheses place tyrannosaurin origins in Asia, or western North America (Larami...

Dromaeosaurids (Theropoda: Dromaeosauridae), a group of dynamic, swift predators, have a sparse fossil record, particularly at the end of the Cretaceous Period. The recently described Dineobellator notohesperus, consisting of a partial skeleton from the Upper Cretaceous (Maastrichtian) of New Mexico, is the only diagnostic dromaeosaurid to be recov...

A nearly complete skull of a new ceratopsid dinosaur, Bisticeratops froeseorum, is described from the Farmington Member of the Kirtland Formation (late Campanian, Upper Cretaceous) of New Mexico. Bisticeratops is distinguished by several diagnostic cranial characters, including those of the premaxilla (stepped dorsal margin), maxilla (short jugal p...

The Connecticut Valley in southwestern Massachusetts is famous for numerous dinosaur tracksites dated to the Early Jurassic. These are in the East Berlin Formation and Portland Group of the Newark Supergroup. The tracksites from the East Berlin Formation are located in the towns of Holyoke and West Springfield, whereas those from the Portland Group...

The horned dinosaurs (Ceratopsidae) were a diverse family of herbivorous dinosaurs originating in the Late Cretaceous in western North America (Laramidia). As one of the most species-rich dinosaur groups, their diversity and distribution are important to understanding Cretaceous dinosaur evolution. Ceratopsids have previously been hypothesized to h...

An associated incomplete skeleton of a ceratopsid dinosaur from the Campanian deposits of the Allison Member of the Menefee Formation in New Mexico, USA is described. Although it was originally described over two decades ago, newly prepared portions of the Menefee Formation skeleton and reinterpretations of previously known morphology, in addition...

An isolated anterior left dentary, proximal caudal centrum and an isolated right femur pertaining to adult, subadult and juvenile tyrannosaurid dinosaurs from the Upper Cretaceous deposits of the San Juan Basin in New Mexico preserve several bite marks and other feeding traces made by another tyrannosaurid. The dentary was recovered from the Ne-nah...

A new ceratopsid dinosaur, Crittendenceratops krzyzanowskii, is described from the Fort Crittenden Formation (Upper Cretaceous) of southeastern Arizona, and is based on two individuals consisting of partial cranial material recovered from the same stratigraphic unit. A phylogenetic analysis of ceratopsids recovers Crittendenceratops as a member of...

Several isolated teeth of tyrannosaurid dinosaurs from the Upper Campanian Two Medicine Formation of Montana are described. The teeth were found at the Flaming Cliffs, the Landslide Butte, and the Willow Creek Anticline localities. Some teeth are incomplete, whereas others are nearly complete. Extensive wear facets are preserved on most teeth. The...

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 Tyrannosauroid...

An isolated right dentary of the tyrannosaurid Gorgosaurus libratus in the Fukui Prefectural Dinosaur Museum found in the Dinosaur Park Formation in southern Alberta, Canada, is described. The referral of the dentary to G. libratus is based on several morphological features, including the lack of the posteroventral transitional point in the anterio...

North-south provinciality among Campanian and/or Maastrichtian vertebrates, especially dinosaurs, in the Western Interior basin of North America (specifically, between West Texas and southern Alberta, Canada) has been accepted by many vertebrate paleontologists for about 30 years. However, a critical review indicates that the case for provinciality...

Cheliceratichnus lockleyi ichnogen. nov. et ichnosp. nov. is a new ichnotaxon of arthropod resting trace (cubichnium) from the Lower Jurassic (Hettangian) East Berlin Formation in Holyoke, Massachusetts, USA. The trace fossil is preserved as showing many of the external anatomical features of the exoskeleton, which resemble those of some chelicerat...

The holotype of Camptonotus amplus Marsh, 1879, the right pes YPM VP.1879 from the Morrison Formation (Upper Jurassic) of Wyoming, USA, has long been referred to the Morrison ornithopod dinosaur Camptosaurus Marsh, 1885. However, the pointed proximal end of Mt I did not reach the tarsus, but was attached by ligaments to the mid-shaft of Mt II as in...

The dinosaur remains from the Upper Cretaceous Lance Formation of Wyoming, USA, have been known since 1870. Most of the fossils that are attributed to theropod dinosaurs are fragmentary skeletons consisting of cranial, axial and appendicular elements, and many isolated teeth are also known. The largest known theropod of the Lance Formation dinosaur...

Numerous new trackways of the small, ornithischian dinosaurs ichnogenus Anomoepus were discovered in the Lower Jurassic (Hettangian) East Berlin Formation in Holyoke, Massachusetts. This new material consists of 16 trackways, on two bedding surfaces 1.5 cm apart, all in close proximity to each other. The abundant pedal and manual impressions have w...

In 1844-1846, Alfred T. King (1813-1858) gave ichnotaxonomic names to what he believed to be fossil footprints from the Pennsylvanian strata of Westmoreland County in western Pennsylvania. In 1846, the famous British geologist Charles Lyell examined these footprints and some of their localities and concluded that most were manmade artifacts (Native...

A Portland Formation Lower Jurassic (Hettangian) dinosaur tracksite in Granby, Massachusetts, USA, has yielded a diverse dinosaur footprint assemblage. The tracksite preserves 140 theropod dinosaur footprints, ranging in length from 15 to 35 cm; the ichnofauna includes Anchisauripus, Eubrontes, Grallator and other extremely small theropod dinosaur...

In 1953, J. T. Gregory and D. Techter of the Yale Peabody Museum of Natural History discovered a partially preserved theropod skeleton in the Morrison Formation (Late Tithonian) of McElmo Canyon in Montezuma County, Colorado, U.S.A. The specimen consists of several well-preserved cranial, axial, and appendicular elements, some of which are still un...