scholarly journals Nestling-sized hadrosaurine cranial material from the Hell Creek Formation of northeastern Montana, USA, with an analysis of cranial ontogeny in Edmontosaurus annectens

PaleoBios ◽  
2019 ◽  
Vol 36 ◽  
Author(s):  
Mateusz Wosik ◽  
Mark B. Goodwin ◽  
David C. Evans
Keyword(s):  
Hell Creek Formation ◽  
Cranial Ontogeny

LIFE AFTER IMPACT: A REMARKABLE MAMMAL BURROW FROM THE CHICXULUB AFTERMATH IN THE HELL CREEK FORMATION, NORTH DAKOTA

2017 ◽  
Author(s):  
Robert A. DePalma ◽  
◽  
David A. Burnham ◽  
David A. Burnham ◽  
David A. Burnham ◽  
...  
Keyword(s):  
North Dakota ◽  
Hell Creek Formation

Evolution of Cranial Ontogeny in South American Canids (Carnivora: Canidae)

2021 ◽  
Author(s):  
Valentina Segura ◽  
Guillermo H. Cassini ◽  
Francisco J. Prevosti
Keyword(s):  
South American ◽  
Cranial Ontogeny

scholarly journals Ngwevu intloko: a new early sauropodomorph dinosaur from the Lower Jurassic Elliot Formation of South Africa and comments on cranial ontogeny in Massospondylus carinatus

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7240 ◽  
Author(s):  
Kimberley E.J. Chapelle ◽  
Paul M. Barrett ◽  
Jennifer Botha ◽  
Jonah N. Choiniere
Keyword(s):  
South Africa ◽  
New Species ◽  
Sexual Dimorphism ◽  
New Genus ◽  
Lower Jurassic ◽  
Early Jurassic ◽  
Adult Size ◽  
Minimum Age ◽  
Cranial Ontogeny ◽  
Morphological Differences

Our knowledge of Early Jurassic palaeobiodiversity in the upper Elliot Formation of South Africa has increased markedly in recent years with the discovery of new fossils, re-assessments of previously collected material and a better understanding of Stormberg Group stratigraphy. Here, Ngwevu intloko, a new genus of upper Elliot basal sauropodomorph is named on the basis of a complete skull and partial skeleton (BP/1/4779) previously assigned to Massospondylus carinatus. It can be distinguished from all other basal sauropodomorphs by a combination of 16 cranial and six postcranial characters. The new species is compared to a small ontogenetic series of M. carinatus as well as to a range of closely related taxa. Taphonomic deformation, sexual dimorphism and ontogeny are rejected as possible explanations for the morphological differences present between BP/1/4779 and other taxa. Osteohistological examination reveals that BP/1/4779 had nearly reached adult size at the time of its death at a minimum age of 10 years.

scholarly journals Unexpected resilience of species with temperature-dependent sex determination at the Cretaceous–Palaeogene boundary

2010 ◽  
Vol 7 (2) ◽  
pp. 295-298 ◽  
Author(s):  
Sherman Silber ◽  
Jonathan H. Geisler ◽  
Minjin Bolortsetseg
Keyword(s):  
Climate Change ◽  
Sex Ratio ◽  
Sex Determination ◽  
Volcanic Eruptions ◽  
Egg Laying ◽  
Molecular Clocks ◽  
Temperature Dependent ◽  
Hell Creek Formation ◽  
Male Preponderance ◽  
Genotypic Sex Determination

It has been suggested that climate change at the Cretaceous–Palaeogene (K–Pg) boundary, initiated by a bolide impact or volcanic eruptions, caused species with temperature-dependent sex determination (TSD), including dinosaurs, to go extinct because of a skewed sex ratio towards all males. To test this hypothesis, the sex-determining mechanisms (SDMs) of Cretaceous tetrapods of the Hell Creek Formation (Montana, USA) were inferred using parsimony optimizations of SDMs on a tree, including Hell Creek species and their extant relatives. Although the SDMs of non-avian dinosaurs could not be inferred, we were able to determine the SDMs of 62 species; 46 had genotypic sex determination (GSD) and 16 had TSD. The TSD hypothesis for extinctions performed poorly, predicting between 32 and 34 per cent of survivals and extinctions. Most surprisingly, of the 16 species with TSD, 14 of them survived into the Early Palaeocene. In contrast, 61 per cent of species with GSD went extinct. Possible explanations include minimal climate change at the K–Pg, or if climate change did occur, TSD species that survived had egg-laying behaviour that prevented the skewing of sex ratios, or had a sex ratio skewed towards female rather than male preponderance. Application of molecular clocks may allow the SDMs of non-avian dinosaurs to be inferred, which would be an important test of the pattern discovered here.

Metatarsals of a large caenagnathid cf. Anzu wyliei (Theropoda: Oviraptorosauria) from the Hell Creek Formation in South Dakota, U.S.A.

2021 ◽  
Author(s):  
Kousuke Tsujimura ◽  
Makoto Manabe ◽  
Yumiko Chiba ◽  
Takanobu Tsuihiji
Keyword(s):  
South Dakota ◽  
Present Finding ◽  
Hell Creek Formation ◽  
Anatomical Information ◽  
Present Description ◽  
Bone Beds

Isolated metatarsals III and IV of a caenagnathid theropod likely referable to Anzu wyliei are described from a locality of the Hell Creek Formation in northwestern South Dakota of the U.S.A. These bones are missing from the holotype and only partial shafts have been described for a specimen referable to this species. Accordingly, the present description adds further anatomical information on this already well-known species of Caenagnathidae. The present finding also demonstrates the significance of isolated or fragmentary specimens found in multitaxic bone beds.

scholarly journals A juvenile cf. Edmontosaurus annectens (Ornithischia, Hadrosauridae) femur documents a poorly represented growth stage for this taxon

2019 ◽  
Vol 7 ◽  
Author(s):  
Andrew Farke ◽  
Eunice Yip
Keyword(s):  
Size Range ◽  
Femoral Shaft ◽  
Relative Increase ◽  
Slight Reduction ◽  
Femur Length ◽  
Hell Creek Formation ◽  
Juvenile Specimen ◽  
Juvenile Individual ◽  
Asymmetrical Shape ◽  
Distinct Separation

A nearly complete, but isolated, femur of a small hadrosaurid from the Hell Creek Formation of Montana is tentatively referred to Edmontosaurus annectens. At 28 cm long, the element can be classified as that from an “early juvenile” individual, approximately 24 percent of the maximum known femur length for this species. Specimens from this size range and age class have not been described previously for E. annectens. Notable trends with increasing body size include increasingly distinct separation of the femoral head and greater trochanter, relative increase in the size of the cranial trochanter, a slight reduction in the relative breadth of the fourth trochanter, and a relative increase in the prominence of the cranial intercondylar groove. The gross profile of the femoral shaft is fairly consistent between the smallest and largest individuals. Although an ontogenetic change from relatively symmetrical to an asymmetrical shape in the fourth trochanter has been suggested previously, the new juvenile specimen shows an asymmetric fourth trochanter. Thus, there may not be a consistent ontogenetic pattern in trochanteric morphology. An isometric relationship between femoral circumference and femoral length is confirmed for Edmontosaurus. Overall ontogenetic trends in the femur of Edmontosaurus are concordant with patterns seen in other Hadrosauridae, supporting a fairly conserved pattern of development for this element within the clade.

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