Haemal arch

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Haemal arches of Nothronychus Nothronychus chevrons.png
Haemal arches of Nothronychus

A haemal arch, also known as a chevron, is a bony arch on the ventral side of a tail vertebra of a vertebrate. The canal formed by the space between the arch and the vertebral body is the haemal canal. A spinous ventral process emerging from the haemal arch is referred to as the haemal spine.

Blood vessels to and from the tail run through the arch. In reptiles, the caudofemoralis longus muscle, one of the main muscles involved in locomotion, attaches to the lateral sides of the haemal arches. [1]

In 1956, Alfred Sherwood Romer hypothesized that the position of the first haemal arch was sexually dimorphic in crocodilians and dinosaurs. [2] However, subsequent research established that the size and position of the first haemal arch was not sexually dimorphic in crocodilians and found no evidence of significant variation in tyrannosaurid dinosaurs, indicating that haemal arches could not be used to distinguish between sexes after all. [3]

Haemal arches play an important role in the taxonomy of sauropod dinosaurs, as sauropods exhibit a wide range of morphologies of the haemal arches. [1] In 1878, Othniel Marsh named the sauropod Diplodocus after the distinctive shape of its haemal arches, which were forked to have both an anterior and posterior process. [4] Though once thought to be a specialized characteristic of Diplodocus and its close relatives, forked chevrons are now known to have been widespread among sauropod dinosaurs, although titanosauriform sauropods returned to the unforked condition. [5]

Related Research Articles

<i>Apatosaurus</i> Sauropod dinosaur genus from Late Jurassic period

Apatosaurus is a genus of herbivorous sauropod dinosaur that lived in North America during the Late Jurassic period. Othniel Charles Marsh described and named the first-known species, A. ajax, in 1877, and a second species, A. louisae, was discovered and named by William H. Holland in 1916. Apatosaurus lived about 152 to 151 million years ago (mya), during the late Kimmeridgian to early Tithonian age, and are now known from fossils in the Morrison Formation of modern-day Colorado, Oklahoma, New Mexico, Wyoming, and Utah in the United States. Apatosaurus had an average length of 21–23 m (69–75 ft), and an average mass of 16.4–22.4 t. A few specimens indicate a maximum length of 11–30% greater than average and a mass of approximately 33 t.

<i>Mamenchisaurus</i> Sauropod dinosaur genus from Late Jurassic-Early Cretaceous Period

Mamenchisaurus is a genus of sauropod dinosaur known for their remarkably long necks which made up nearly half the total body length. Numerous species have been assigned to the genus; however, many of these might be questionable. Fossils have been found in the Sichuan Basin and Yunnan Province in China. Several species are from the Upper Shaximiao Formation whose geologic age is uncertain. However, evidence suggests that this be no earlier than the Oxfordian stage of the Late Jurassic. M. sinocanadorum dates to the Oxfordian stage and M. anyuensis to the Aptian stage of the Early Cretaceous around 114.4 mya. Most species were medium to large size sauropods, around 15 to 26 meters in length and possibly up to 35 meters (115 ft) based on two undescribed vertebrae.

<i>Camarasaurus</i> Camarasaurid sauropod dinosaur genus from Late Jurassic Period

Camarasaurus was a genus of quadrupedal, herbivorous dinosaurs and is the most common North American sauropod fossil. Its fossil remains have been found in the Morrison Formation, dating to the Late Jurassic epoch, between 155 and 145 million years ago.

<span class="mw-page-title-main">Diplodocidae</span> Extinct family of dinosaurs

Diplodocids, or members of the family Diplodocidae, are a group of sauropod dinosaurs. The family includes some of the longest creatures ever to walk the Earth, including Diplodocus and Supersaurus, some of which may have reached lengths of up to 42 metres (138 ft).

<i>Barosaurus</i> Diplodocid sauropod dinosaur genus from Upper Jurassic Period

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<i>Cetiosauriscus</i> Genus of reptiles (fossil)

Cetiosauriscus is a genus of sauropod dinosaur that lived between 166 and 164 million years ago during the Callovian in what is now England. A herbivore, Cetiosauriscus had — by sauropod standards — a moderately long tail, and longer forelimbs, making them as long as its hindlimbs. It has been estimated as about 15 m (49 ft) long and between 4 and 10 t in weight.

<i>Euhelopus</i> Extinct genus of dinosaurs

Euhelopus is a genus of sauropod dinosaur that lived between 145 and 133 million years ago during the Berriasian and Valanginian stages of the Early Cretaceous in what is now Shandong Province in China. It was a large quadrupedal herbivore. Like sauropods such as brachiosaurs and titanosaurs, Euhelopus had longer forelegs than hind legs. This discovery was paleontologically significant because it represented the first dinosaur scientifically investigated from China: seen in 1913, rediscovered in 1922, and excavated in 1923 and studied by T'an during the same year. Unlike most sauropod specimens, it has a relatively complete skull.

<i>Brontosaurus</i> Genus of diplodocid sauropod dinosaur

Brontosaurus is a genus of herbivorous sauropod dinosaur that lived in present-day United States during the Late Jurassic period. It was described by American paleontologist Othniel Charles Marsh in 1879, the type species being dubbed B. excelsus, based on a partial skeleton lacking a skull found in Como Bluff, Wyoming. In subsequent years, two more species of Brontosaurus were named: B. parvus in 1902 and B. yahnahpin in 1994. Brontosaurus lived about 156 to 146 million years ago (mya) during the Kimmeridgian and Tithonian ages in the Morrison Formation of what is now Utah and Wyoming. For decades, the animal was thought to have been a taxonomic synonym of its close relative Apatosaurus, but a 2015 study by Emmanuel Tschopp and colleagues found it to be distinct. It has seen widespread representation in popular culture, being the archetypal "long-necked" dinosaur in general media.

<i>Algoasaurus</i> Extinct genus of dinosaurs

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<i>Andesaurus</i> Extinct genus of dinosaurs

Andesaurus is a genus of basal titanosaurian sauropod dinosaur which existed during the middle of the Cretaceous Period in South America. Like most sauropods, belonging to one of the largest animals ever to walk the Earth, it would have had a small head on the end of a long neck and an equally long tail.

<span class="mw-page-title-main">Camarasauridae</span> Extinct family of dinosaurs

Camarasauridae is a family of sauropod dinosaurs. Among sauropods, camarasaurids are small to medium-sized, with relatively short necks. They are visually identifiable by a short skull with large nares, and broad, spatulate teeth filling a thick jaw. Based on cervical vertebrae and cervical rib biomechanics, camarasaurids most likely moved their necks in a vertical, rather than horizontal, sweeping motion, in contrast to most diplodocids.

<span class="mw-page-title-main">Neosauropoda</span> Extinct clade of dinosaurs

Neosauropoda is a clade within Dinosauria, coined in 1986 by Argentine paleontologist José Bonaparte and currently described as Saltasaurus loricatus, Diplodocus longus, and all animals directly descended from their most recent common ancestor. The group is composed of two subgroups: Diplodocoidea and Macronaria. Arising in the early Jurassic and persisting until the Cretaceous-Paleogene extinction event, Neosauropoda contains the majority of sauropod genera, including genera such as Apatosaurus, Brachiosaurus, and Diplodocus. It also includes giants such as Argentinosaurus, Patagotitan and Sauroposeidon, and its members remain the largest land animals ever to have lived.

<i>Camarasaurus grandis</i> Extinct species of dinosaur

Camarasaurus grandis is an extinct species of sauropod dinosaur in the genus that lived during the Jurassic in what is now the western United States. It is the geologically oldest of the four species of the genus Camarasaurus.

<span class="mw-page-title-main">Apatosaurinae</span> Extinct subfamily of dinosaurs

Apatosaurinae is a subfamily of diplodocid sauropods, an extinct group of large, quadrupedal dinosaurs, the other subfamily in Diplodocidae being Diplodocinae. Apatosaurines are distinguished by their more robust, stocky builds and shorter necks proportionally to the rest of their bodies. Several fairly complete specimens are known, giving a comprehensive view of apatosaurine anatomy.

<i>Diplodocus</i> Genus of diplodocid sauropod dinosaurs (fossil)

Diplodocus was a genus of diplodocid sauropod dinosaurs, whose fossils were first discovered in 1877 by S. W. Williston. The generic name, coined by Othniel Charles Marsh in 1878, is a Neo-Latin term derived from Greek διπλός (diplos) "double" and δοκός (dokos) "beam", in reference to the double-beamed chevron bones located in the underside of the tail, which were then considered unique.

Sexual dimorphism in dinosaurs refers to the different physical characteristics of male and female dinosaurs of the same species. This means that the male and female dinosaurs of a species may differ in size, color, shape, or they may even look like a completely different species altogether, such as in the case of the anglerfish. These differing physical characteristics can also be the deciding factor for choosing a mate or can be helpful for blending into the surrounding environment. Researching sexual dimorphism in extinct dinosaurs can be extremely difficult because suitable tissue and skeletal samples are required for testing, and most fossils and other samples have been damaged by decomposition and fossilization.

<span class="mw-page-title-main">Vertebral column</span> Bony structure found in vertebrates

The vertebral column, also known as the backbone or spine, is the core part of the axial skeleton in vertebrate animals. The vertebral column is the defining characteristic of vertebrate endoskeleton in which the notochord found in all chordates has been replaced by a segmented series of mineralized irregular bones called vertebrae, separated by fibrocartilaginous intervertebral discs. The dorsal portion of the vertebral column houses the spinal canal, a cavity formed by alignment of the neural arches that encloses and protects the spinal cord.

This glossary explains technical terms commonly employed in the description of dinosaur body fossils. Besides dinosaur-specific terms, it covers terms with wider usage, when these are of central importance in the study of dinosaurs or when their discussion in the context of dinosaurs is beneficial. The glossary does not cover ichnological and bone histological terms, nor does it cover measurements.

<i>Dreadnoughtus</i> Extinct genus of dinosaur

Dreadnoughtus is a genus of titanosaurian sauropod dinosaur containing a single species, Dreadnoughtus schrani. D. schrani is known from two partial skeletons discovered in Upper Cretaceous rocks of the Cerro Fortaleza Formation in Santa Cruz Province, Argentina. It is one of the largest terrestrial vertebrates known, with the immature type specimen measuring 26 metres (85 ft) in total body length and weighing 48–49 metric tons. D. schrani is known from more complete skeletons than any other gigantic titanosaurian.

Triunfosaurus is a genus of somphospondylan sauropod dinosaur from the Early Cretaceous of Brazil. It contains a single species, T. leonardii, described by Carvalho et al. in 2017. As a genus, Triunfosaurus can be distinguished from all other titanosaurs by the unique proportions of its ischium. It was initially described as a basal titanosaur, making it the earliest basal titanosaur known; however, subsequent research questioned the identification of the taxon as a titanosaur, instead reassigning it to the Somphospondyli.

References

  1. 1 2 Otero, Alejandro; Gallina, Pablo Ariel; Canale, Juan Ignacio; Haluza, Alejandro (2011-10-31). "Sauropod haemal arches: morphotypes, new classification and phylogenetic aspects". Historical Biology: 1–14. doi:10.1080/08912963.2011.618269. ISSN   1029-2381. S2CID   84286012 . Retrieved 2017-03-07.
  2. Romer, Alfred Sherwood (1956). The Osteology of the Reptiles. University of Chicago Press.
  3. Erickson, Gregory M.; Lappin, A. Kristopher; Larson, Peter (2005-11-20). "Androgynous rex – The utility of chevrons for determining the sex of crocodilians and non-avian dinosaurs". Zoology. 108 (4): 277–286. doi:10.1016/j.zool.2005.08.001. ISSN   0944-2006. PMID   16351976 . Retrieved 2020-08-20.
  4. Marsh, O. C. (1878). "Principal characters of American Jurassic dinosaurs". American Journal of Science. 3. 16: 411–416.
  5. Upchurch, Paul; Barrett, Paul M.; Dodson, Peter (2004). "Sauropoda". In Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (eds.). The Dinosauria (2 ed.). Berkeley: University of California Press. pp. 259–322. ISBN   0-520-24209-2.