scholarly journals A JUVENILE METATARSAL OF CF. DASPLETOSAURUS TOROSUS: IMPLICATIONS FOR ONTOGENY IN TYRANNOSAURID THEROPODS

2021 ◽  
pp. 15-22
Author(s):  
CHAN-GYU YUN
Keyword(s):  
Fossil Record ◽  
Growth Stages ◽  
Large Juvenile ◽  
Dinosaur Park Formation ◽  
Young Growth

A well preserved, but isolated metatarsal III of a tyrannosaurid dinosaur, originating probably from the Dinosaur Park Formation of Alberta, Canada, is tentatively referred to Daspletosaurus torosus. The size of the specimen suggests that it likely comes from a large juvenile, since the width of the distal end is about 63 % of that of a much larger individual. The morphology of the specimen supports the recently suggested hypotheses that apomorphies of tyrannosaurid taxa may have developed at young growth stages, and that juveniles of albertosaurines and tyrannosaurines may be easier to distinguish from one another than previously thought. Additionally, the specimen reported here is important in that it provides an addition to the very poor juvenile fossil record of Daspletosaurus.

Anatomical, morphometric, and stratigraphic analyses of theropod biodiversity in the Upper Cretaceous (Campanian) Dinosaur Park Formation

2021 ◽  
pp. 1-15
Author(s):  
Thomas M. Cullen ◽  
Lindsay Zanno ◽  
Derek W. Larson ◽  
Erinn Todd ◽  
Philip J. Currie ◽  
...  
Keyword(s):  
High Resolution ◽  
North America ◽  
Fossil Record ◽  
Upper Cretaceous ◽  
Environmental Changes ◽  
Morphometric Analyses ◽  
Variable Distribution ◽  
Taxic Diversity ◽  
Dinosaur Park Formation ◽  
Broad Scale

The Dinosaur Park Formation (DPF) of Alberta, Canada, has produced one of the most diverse dinosaur faunas, with the record favouring large-bodied taxa, in terms of number and completeness of skeletons. Although small theropods are well documented in the assemblage, taxonomic assessments are frequently based on isolated, fragmentary skeletal elements. Here we reassess DPF theropod biodiversity using morphological comparisons, high-resolution biostratigraphy, and morphometric analyses, with a focus on specimens/taxa originally described from isolated material. In addition to clarifying taxic diversity, we test whether DPF theropods preserve faunal zonation/turnover patterns similar to those previously documented for megaherbivores. Frontal bones referred to a therizinosaur (cf. Erlikosaurus), representing among the only skeletal record of the group from the Campanian–Maastrichtian (83–66 Ma) fossil record of North America, plot most closely to troodontids in morphospace, distinct from non-DPF therizinosaurs, a placement supported by a suite of troodontid anatomical frontal characters. Postcranial material referred to cf. Erlikosaurus in North America is also reviewed and found most similar in morphology to caenagnathids, rather than therizinosaurs. Among troodontids, we document considerable morphospace and biostratigraphic overlap between Stenonychosaurus and the recently described Latenivenatrix, as well as a variable distribution of putatively autapomorphic characters, calling the validity of the latter taxon into question. Biostratigraphically, there are no broad-scale patterns of faunal zonation similar to those previously documented in ornithischians from the DPF, with many theropods ranging throughout much of the formation and overlapping extensively, possibly reflecting a lack of sensitivity to environmental changes, or other cryptic ecological or evolutionary factors.

Ontogeny in the fossil record: diversification of body plans and the evolution of “aberrant” symmetry in Paleozoic echinoderms

Paleobiology ◽  
2007 ◽  
Vol 33 (1) ◽  
pp. 149-163 ◽  
Author(s):  
Colin D. Sumrall ◽  
Gregory A. Wray
Keyword(s):  
Great Reduction ◽  
Fossil Record ◽  
Evolutionary History ◽  
Total Loss ◽  
Cambrian Explosion ◽  
Growth Stages ◽  
Ecological Constraints ◽  
Fivefold Symmetry ◽  
Primary Body ◽  
History Of

Echinoderms have long been characterized by the presence of ambulacra that exhibit pentaradiate symmetry and define five primary body axes. In reality, truly pentaradial ambulacral symmetry is a condition derived only once in the evolutionary history of echinoderms and is restricted to eleutherozoans, the clade that contains most living echinoderm species. In contrast, early echinoderms have a bilaterally symmetrical 2-1-2 arrangement, with three ambulacra radiating from the mouth. Branching of the two side ambulacra during ontogeny produces the five adult rays. During the Cambrian Explosion and Ordovician Radiation, some 30 clades of echinoderms evolved, many of which have aberrant ambulacral systems with one to four rays. Unfortunately, no underlying model has emerged that explains ambulacral homologies among disparate forms. Here we show that most Paleozoic echinoderms are characterized by uniquely identifiable ambulacra that develop in three distinct postlarval stages. Nearly all “aberrant” echinoderm morphologies can be explained by the paedomorphic ambulacra reduction (PAR) model through the loss of some combination of these growth stages during ontogeny. Superficially similar patterns of ambulacral reduction in distantly related clades have resulted from the parallel loss of homologous ambulacra during ontogeny. Pseudo-fivefold symmetry seen in Blastoidea and the true fivefold symmetry seen in Eleutherozoa result from great reduction and total loss, respectively, of the 2–1–2 symmetry early in ontogeny. These ambulacral variations suggest that both developmental and ecological constraints affect the evolution of novel echinoderm body plans.

The early growth stages and adult structure of the lophophore of Macandrevia cranium (Müller) (Brachiopoda, Dallinidae)

1959 ◽  
Vol 38 (2) ◽  
pp. 335-350 ◽  
Author(s):  
D. Atkins
Keyword(s):  
Early Growth ◽  
Growth Stages ◽  
Early Stages ◽  
Young Growth

Although it has been stated (Thomson, 1927, p. 234; Elliott, 1953, p. 264) that the descending branches of the loop in dallinids, so far as is known, grow from the crura only, yet figures supporting this statement have not so far been published, not even by Beecher (1895) who described the very early stages of lophophore and loop in Dallinella (=Terebratalia) obsoleta (Dall). Tiny specimens of Macandrevia cranium dredged by R. V. ‘Sarsia’ have now made it possible for such figures to be published. It is a point of some importance as it is one of the characters given by Thomson (1927, p. 234) as distinguishing the Dallininae from the Mühlfeldtiinae (= Megerliinae Muir-Wood, 1955) and the Magellaniinae (= Terebratellinae, see Muir-Wood, 1955), for in the two latter groups the descending branches of the loop grow from both crura and septum to unite in the middle. At the time Thomson was writing, young growth stages of the loop of a member of the Laqueinae were not known. Since then, Konjoukova (1948, 1957) has studied the development of Laqueus californicus—which she placed in the Dallininae—and according to her the descending branches on reaching the septum join with it. She does not, however, figure any intermediate stages between absence of descending branches and complete ones. In 1941 Laqueinae was raised to family rank by Yabe and Hatai (see Muir-Wood, 1955, p. 93).

First report of protoceratopsians (Neoceratopsia) from the Late Cretaceous Judith River Group, Alberta, Canada

1998 ◽  
Vol 35 (7) ◽  
pp. 820-826 ◽  
Author(s):  
Michael J Ryan ◽  
Philip J Currie
Keyword(s):  
North America ◽  
Late Cretaceous ◽  
Fossil Record ◽  
Coastal Environments ◽  
First Report ◽  
Skeletal Material ◽  
First Occurrence ◽  
Dinosaur Park Formation ◽  
Milk River Formation

Protoceratopsians are best known in North America from associated skeletal material of Montanoceratops from the early Maastrichtian of Montana and Campanian of Alberta and Leptoceratops from the late Maastrichtian of Alberta and Wyoming. We report here the first occurrence of protoceratopsian elements from the middle Campanian (Dinosaur Park Formation) of Alberta. The specimens consist of a fragmentary right dentary and an almost complete left dentary which can be referred to Leptoceratops sp. Recent examination of Albertan microvertebrate material has identified cf. protoceratopsians teeth from the latest Santonian (Milk River Formation), extending the record of Albertan protoceratopsians back almost 20 million years. The rarity of these small ornithischians in the fossil record of Alberta may have been due to ecological exclusion from the wet, coastal environments that were preferred by the larger, more abundant ceratopsids.

scholarly journals Bite marks on the frill of a juvenile Centrosaurus from the Late Cretaceous Dinosaur Provincial Park Formation, Alberta, Canada

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5748 ◽  
Author(s):  
David W.E. Hone ◽  
Darren H. Tanke ◽  
Caleb M. Brown
Keyword(s):  
Late Cretaceous ◽  
Fossil Record ◽  
Scientific Literature ◽  
Documented Case ◽  
Critical Information ◽  
Bite Marks ◽  
Record Data ◽  
Dinosaur Park Formation ◽  
Provincial Park ◽  
Rare Instance

Bite marks on bones can provide critical information about interactions between carnivores and animals they consumed (or attempted to) in the fossil record. Data from such interactions is somewhat sparse and is hampered by a lack of records in the scientific literature. Here, we present a rare instance of feeding traces on the frill of a juvenile ceratopsian dinosaur from the late Campanian Dinosaur Park Formation of Alberta. It is difficult to determine the likely tracemaker(s) but the strongest candidate is a small-bodied theropod such as a dromaeosaur or juvenile tyrannosaur. This marks the first documented case of carnivore consumption of a juvenile ceratopsid, but may represent scavenging as opposed to predation.

scholarly journals A Reevaluation of Sexual Dimorphism in the Postcranium of the Chasmosaurine Ceratopsid Chasmosaurus belli (Dinosauria: Ornithischia)

2006 ◽  
Vol 120 (4) ◽  
pp. 403 ◽  
Author(s):  
Jordan C. Mallon ◽  
Robert B. Holmes
Keyword(s):  
Sexual Dimorphism ◽  
Fossil Record ◽  
Statistical Significance ◽  
Separate Species ◽  
Moderate Amount ◽  
Show Evidence ◽  
Dinosaur Park Formation

The sexual dimorphism attributed to Chasmosaurus belli by Sternberg (1927) is revisited and reevaluated. A reexamination of the two specimens originally considered by Sternberg reveals that they are less complete than first suggested, with only a moderate amount of overlapping material between them. Only a few of the postcranial elements (humeri, sternal plates, and presacral vertebrae) show evidence of dimorphism, the significance of which is either doubtful or equivocal. Instead of representing sexual dimorphs, it is likely that the two specimens belong to separate species, C. belli and C. russelli, as evidenced by their distinct frill morphologies and by their stratigraphic segregation within the Dinosaur Park Formation of Alberta. These findings emphasize the need to remain sceptical about claims advocating sexual dimorphism in the fossil record in the absence of statistical significance or stratigraphic control.

Ediacara growing pains: modular addition and development in Dickinsonia costata

Paleobiology ◽  
2021 ◽  
pp. 1-16
Author(s):  
Scott D. Evans ◽  
James G. Gehling ◽  
Douglas H. Erwin ◽  
Mary L. Droser
Keyword(s):  
Body Size ◽  
Fossil Record ◽  
South Australia ◽  
Growth Stages ◽  
Genetic Pathways ◽  
Morphogen Gradients ◽  
Ediacara Biota ◽  
Growing Pains ◽  
Competing Hypotheses ◽  
The Relationship

Abstract Constraining patterns of growth using directly observable and quantifiable characteristics can reveal a wealth of information regarding the biology of the Ediacara biota—the oldest macroscopic, complex community-forming organisms in the fossil record. However, these rely on individuals captured at an instant in time at various growth stages, and so different interpretations can be derived from the same material. Here we leverage newly discovered and well-preserved Dickinsonia costata Sprigg, 1947 from South Australia, combined with hundreds of previously described specimens, to test competing hypotheses for the location of module addition. We find considerable variation in the relationship between the total number of modules and body size that cannot be explained solely by expansion and contraction of individuals. Patterns derived assuming new modules differentiated at the anterior result in numerous examples in which the oldest module(s) must decrease in size with overall growth, potentially falsifying this hypothesis. Observed polarity as well as the consistent posterior location of defects and indentations support module formation at this end in D. costata. Regardless, changes in repeated units with growth share similarities with those regulated by morphogen gradients in metazoans today, suggesting that these genetic pathways were operating in Ediacaran animals.

Neuron-glia relationship during the early postembryonic development of the nervous system in some oligochaetes

1978 ◽  
Vol 36 (2) ◽  
pp. 600-601
Author(s):  
Wiktor Djaczenko ◽  
Carmen Calenda Cimmino
Keyword(s):  
Nervous System ◽  
Glial Cells ◽  
Early Period ◽  
Postembryonic Development ◽  
Ruthenium Red ◽  
The Body ◽  
Tubifex Tubifex ◽  
Growth Stages ◽  
Cell Processes ◽  
Cytoplasmic Processes

The simplicity of the developing nervous system of oligochaetes makes of it an excellent model for the study of the relationships between glia and neurons. In the present communication we describe the relationships between glia and neurons in the early periods of post-embryonic development in some species of oligochaetes.Tubifex tubifex (Mull. ) and Octolasium complanatum (Dugès) specimens starting from 0. 3 mm of body length were collected from laboratory cultures divided into three groups each group fixed separately by one of the following methods: (a) 4% glutaraldehyde and 1% acrolein fixation followed by osmium tetroxide, (b) TAPO technique, (c) ruthenium red method.Our observations concern the early period of the postembryonic development of the nervous system in oligochaetes. During this period neurons occupy fixed positions in the body the only observable change being the increase in volume of their perikaryons. Perikaryons of glial cells were located at some distance from neurons. Long cytoplasmic processes of glial cells tended to approach the neurons. The superimposed contours of glial cell processes designed from electron micrographs, taken at the same magnification, typical for five successive growth stages of the nervous system of Octolasium complanatum are shown in Fig. 1. Neuron is designed symbolically to facilitate the understanding of the kinetics of the growth process.

Characterisation of multilayer materials using a position-sensitive atom probe

1990 ◽  
Vol 48 (4) ◽  
pp. 624-625
Author(s):  
RAD Mackenzie ◽  
G D W Smith ◽  
A. Cerezo ◽  
J A Liddle ◽  
CRM Grovenor ◽  
...  
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Spatial Information ◽  
Chemical Vapour ◽  
Atom Probe ◽  
Organic Chemical ◽  
Growth Stages ◽  
Multiple Quantum ◽  
Quartz Wool ◽  
Position Sensitive

The position sensitive atom probe (POSAP), described briefly elsewhere in these proceedings, permits both chemical and spatial information in three dimensions to be recorded from a small volume of material. This technique is particularly applicable to situations where there are fine scale variations in composition present in the material under investigation. We report the application of the POSAP to the characterisation of semiconductor multiple quantum wells and metallic multilayers.The application of devices prepared from quantum well materials depends on the ability to accurately control both the quantum well composition and the quality of the interfaces between the well and barrier layers. A series of metal organic chemical vapour deposition (MOCVD) grown GaInAs-InP quantum wells were examined after being prepared under three different growth conditions. These samples were observed using the POSAP in order to study both the composition of the wells and the interface morphology. The first set of wells examined were prepared in a conventional reactor to which a quartz wool baffle had been added to promote gas intermixing. The effect of this was to hold a volume of gas within the chamber between growth stages, leading to a structure where the wells had a composition of GalnAsP lattice matched to the InP barriers, and where the interfaces were very indistinct. A POSAP image showing a well in this sample is shown in figure 1. The second set of wells were grown in the same reactor but with the quartz wool baffle removed. This set of wells were much better defined, as can be seen in figure 2, and the wells were much closer to the intended composition, but still with measurable levels of phosphorus. The final set of wells examined were prepared in a reactor where the design had the effect of minimizing the recirculating volume of gas. In this case there was again further improvement in the well quality. It also appears that the left hand side of the well in figure 2 is more abrupt than the right hand side, indicating that the switchover at this interface from barrier to well growth is more abrupt than the switchover at the other interface.

Sign in / Sign up

Export Citation Format

Share Document