In zoology, a tail club is a bony mass at the end of the

tail The tail is the elongated section at the rear end of a bilaterian animal's body; in general, the term refers to a distinct, flexible appendage extending backwards from the midline of the torso. In vertebrate animals that evolution, evolved to los ...

of some

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

s and of some mammals, most notably the

ankylosaurids Ankylosauridae () is a family of armored dinosaurs within Ankylosauria, and is the sister group to Nodosauridae. The oldest known ankylosaurids date to around 122 million years ago and went extinct 66 million years ago during the Cretaceous–Pal ...

and the

glyptodont Glyptodonts are an extinct clade of large, heavily armoured armadillos, reaching up to in height, and maximum body masses of around 2 tonnes. They had short, deep skulls, a fused vertebral column, and a large bony carapace made up of hundreds o ...

s, as well as meiolaniid

turtle Turtles are reptiles of the order (biology), order Testudines, characterized by a special turtle shell, shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Crypt ...

s. It is thought that this was a form of defensive

armour Armour (Commonwealth English) or armor (American English; see American and British English spelling differences#-our, -or, spelling differences) is a covering used to protect an object, individual, or vehicle from physical injury or damage, e ...

or weapon that was used to defend against

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

s, much in the same way as a

thagomizer A thagomizer () is the distinctive arrangement of spike-shaped osteoderms on the tails of some stegosaurian dinosaurs. These spikes are believed to have been a defensive measure against predators. The arrangement of spikes originally had no dis ...

, possessed by

stegosaurid Stegosauria is a group of herbivorous ornithischian dinosaurs that lived during the Jurassic and early Cretaceous periods. Stegosaurian fossils have been found mostly in the Northern Hemisphere (North America, Europe and Asia), Africa and South A ...

s, though at least in glyptodonts it is hypothesized it was used in fighting for mating rights. Among dinosaurs, the club was present mainly in ankylosaurids, although

sauropods Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their b ...

like ''

Shunosaurus ''Shunosaurus'', meaning "Lizard from Sichuan", is a genus of sauropod dinosaur from Late Jurassic ( Oxfordian) beds in Sichuan Province in China, from 161 to 157 Million years ago. The name derives from "Shu", an ancient name for the Sichuan pr ...

'' and ''

Kotasaurus ''Kotasaurus'' ( ; meaning " Kota Formation lizard") is a genus of sauropod dinosaur from the Early Jurassic period (Sinemurian– Pliensbachian). The only known species is ''Kotasaurus yamanpalliensis''. It was discovered in the Kota Formation ...

'' also possessed a tail club.

Victoria Arbour Victoria Megan Arbour is a Canadian evolutionary biologist and vertebrate palaeontologist at Royal BC Museum, where she is Curator of Palaeontology. An "expert on the armoured dinosaurs known as ankylosaurs", Arbour analyzes fossils and create ...

has established that ankylosaurid tails could generate enough force to break bone during impacts. In a separate study, Arbour suggested tail clubs as well as large armoured herbivores as a whole evolve when animals are too large to hide and too small to avoid predation by size alone.

Morphology

In ankylosaurid dinosaurs, the tail club—or "knob"—consists of enlarged and fused

osteoderms Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of Extant taxon, extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, Temnospondyli, ...

, being supported by a "handle" of the far distal vertebrae being stiff and using the

prezygapophyses The articular process or zygapophysis ( + apophysis) of a vertebra is a projection of the vertebra that serves the purpose of fitting with an adjacent vertebra. The actual region of contact is called the ''articular facet''.Moore, Keith L. et al. ...

to inlock, ensuring rigidity.Arbour, Victoria M.; Currie, Philip J. (2015
"Ankylosaurid dinosaur tail clubs evolved through stepwise acquisition of key features"
Journal of Anatomy. 227 (4): 514–523.

References

Mammal anatomy Dinosaur anatomy {{Vertebrate anatomy-stub

Morphology

See also

References