Healed Fractures in the Neural Spines of an Associated Skeleton of Dimetrodon: Implications for Dorsal Sail Morphology and Function

  title={Healed Fractures in the Neural Spines of an Associated Skeleton of Dimetrodon: Implications for Dorsal Sail Morphology and Function},
  author={Elizabeth Rega and Ken Noriega and Stuart S. Sumida and Adam K. Huttenlocker and Andrew H Lee and Brett Kennedy},
Abstract Hyperelongate neural spines forming a prominent dorsal “sail” are known in eight genera distributed between two families of pelycosaurian-grade synapsids. Although the function(s) of the sail remain disputed, most researchers assume that resilient soft tissue stretched between the elongate neural spines, extending to the distal tips. Hypotheses to explain the purpose of the sail have included thermoregulation (Romer & Price, 1940; Bramwell & Fellgett, 1973; Haack, 1986; Tracy et al… 

Investigation of a bone lesion in a gorgonopsian (Synapsida) from the Permian of Zambia and periosteal reactions in fossil non-mammalian tetrapods

A discrete osseous lesion is reported in the forelimb of a late Permian-aged gorgonopsian synapsid, recording reactive periosteal bone deposition and providing insights into the origins and diversity of skeletal healing responses in premammalian synapsids.

The First Healed Bite Mark and Embedded Tooth in the Snout of a Middle Permian Gorgonopsian (Synapsida: Therapsida)

This work describes, for the first time, the occurrence of a tooth embedded in the snout of a gorgonopsian, surrounded by a bony callus, which demonstrates that the animal was still alive after the attack and healed.

A new long-spined dinosaur from Patagonia sheds light on sauropod defense system

The long, anteriorly bent spines of this new dicraeosaurid sauropod, Bajadasaurus pronuspinax gen. et sp.

Long bone histology indicates sympatric species of Dimetrodon (Lower Permian, Sphenacodontidae)

Histological analysis of newly excavated material from the Briar Creek Bonebed has resolved some of the discretion between these two competing hypothesis, confirming the coexistence of a small (D. natalis) with at least one larger Dimetrodon species.

Regionalization of the axial skeleton predates functional adaptation in the forerunners of mammals

It is proposed that the release of axial respiratory constraints, combined with selection for novel mammalian behaviours in Late Triassic cynodonts, drove the functional divergence of pre-existing morphological regions in synapsid evolution.

Bone histology of varanopids (Synapsida) from Richards Spur, Oklahoma, sheds light on growth patterns and lifestyle in early terrestrial colonizers

It is shown that bone histology has the potential to explain how ballast was shed and the skeleton lightened for terrestrial mobility in ancestral synapsids and their basal amniote kin, as well as how adjustments in postnatal growth influenced the evolution of larger body sizes in the terrestrial frontier.

"Bizarre Structures" Point to Dromaeosaurs as Parasites and a New Theory for the Origin of Avian Flight.

It is proposed that bizarre structures may have served to defend against parasitic dorsal attacks from riding dromaeosaurs, and Frequent dismounts from large living dinosaurs may explain the origin of feathers, gliding and avian flight.

Dimetrodon (Synapsida: Sphenacodontidae) from the cave system at Richards Spur, OK, USA, and a comparison of Early Permian–aged vertebrate paleoassemblages

The morphology and histology of a small neural spine with the distinctive figure-8 shape attributable to Dimetrodon is described for the first time, suggesting not only that this animal was more widespread than previously thought, but that there are different patterns of Early Permian synapsid evolution in different ecological settings.

Nocturnality in synapsids predates the origin of mammals by over 100 million years

Recognizing the complexity of diel activity patterns in non-mammalian synapsids is an important step towards a more nuanced picture of the evolutionary history of behaviour in the synapsid clade.



Comparative anatomy and osteohistology of hyperelongate neural spines in the sphenacodontids Sphenacodon and Dimetrodon (Amniota: Synapsida)

Observed histovariability appears to record the transition from the proximal to the distally protruding portion of the spine, and independent pathological evidence support the existence of a short dorsal crest in Sphenacodon and possibly other basal sphenacodontids.

Neural spine elongation in dinosaurs: sailbacks or buffalo-backs?

  • J. Bailey
  • Environmental Science
    Journal of Paleontology
  • 1997
It is argued here that the neural spines of Ouranosaurus, Spinosaurus, and several other long-spined dinosaurs favor bison-like humps rather than sails, and the insulation properties of humps favor gigantothermy, the most likely thermobiological model for large dinosaurs.

Preparation of fossil bone for histological examination

The technique described has been successfully applied to the bones of dinosaurs and mammal-like reptiles, as well as to archaeological samples ofhuman bone and also to defatted bone of recent taxa and is specifically intended for use on bone.

A New Sphenacodontid Pelycosaur (Synapsida) from the Wichita Group, Lower Permian of North-Central Texas

Two specimens collected recently from the middle Wichita Group of Baylor and Archer Counties, Texas, represent a new sphenacodontid pelycosaur, Ctenorhachis jacksoni, which is distinguished from all other sphenicodontids by neural spines that are only modestly heightened and uniformly blade-like antero-posteriorly.

Aerodynamics and thermoregulatory function of the dorsal sail of Edaphosaurus

Wind tunnel modeling of air flow over a thin sail with laterally projecting cross-bars supports a thermoregulatory interpretation of the sail of Edaphosaurus, and measurements of heat flow in an instrumented model show that cross- Bars increase heat loss from the sail.

The cranial anatomy and relationships of Secodontosaurus, an unusual mammal-like reptile (Synapsida: Sphenacodontidae) from the early Permian of Texas

The cranial anatomy of the Early Permian sphenacodontid synapsid Secodontosaurus is redescribed. There is no evidence for recognition of more than one species of Secodontosaurus, and S. willistoni is

Positive Allometry and the Prehistory of Sexual Selection

The results question the popular view that the elaborated structures of these fossil species evolved as thermoregulatory organs and provide evidence in support of the hypothesis that Pteranodon crests and eupelycosaur sails are among the earliest and most extreme examples of elaborate sexual signals in the evolution of terrestrial vertebrates.

A comparative histological study of fossil and recent bone tissues. Part III.

Part II of the study described in this article is concerned entirely with a description of the histological structure of the bone tissues of fossil and recent reptiles and birds. Methods of

Evolutionary Patterns Among Permo-Triassic Therapsids*

Synapsids form the bulk of tetrapod diversity from Early Permian to Middle Triassic times and thus can provide critical information on the nature of the Permo-Triassic extinction in the terrestrial realm.

The age and locality of the Late Paleozoic vertebrates from El Cobre Canyon, Rio Arriba County, New Mexico

Specimens of the labyrinthodont amphibians Platyhystrix rugosus and Chenoprosopus cf. C. milleri and the pelycosaurian reptile Edaphosaurus cf. E. novomexicanus have been found in El Cobre Canyon,