Brittagnathus

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Brittagnathus
Temporal range: late Famennian
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Sarcopterygii
Clade: Tetrapodomorpha
Clade: Stegocephali
Genus: Brittagnathus
Ahlberg & Clack, 2020
Type species
Brittagnathus minutus
Ahlberg & Clack, 2020

Brittagnathus is an extinct genus of four-limbed vertebrate ("tetrapod") from the Late Devonian of Greenland. It contains a single species, Brittagnathus minutus, which is based on a complete lower jaw recovered from an Acanthostega bonebed in the Britta Dal Formation. It is the fourth named genus of "tetrapod" (more precisely a stem-tetrapod or stegocephalian) from the Late Devonian of Greenland, after Ichthyostega , Acanthostega, and Ymeria . [1]

The jaw is only 4.5 cm (1.8 in.) long, making Brittagnathus the smallest known Devonian "tetrapod". A phylogenetic analysis places it among Carboniferous stegocephalians, particularly the small whatcheeriid Pederpes , rather than the contemporary Devonian stem-tetrapods. This provides support for an origin for Carboniferous-type tetrapods as early as the Devonian. [1]

Related Research Articles

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A tetrapod is any four-limbed vertebrate animal of the superclass Tetrapoda. Tetrapods include all extant and extinct amphibians and amniotes, with the latter in turn evolving into two major clades, the sauropsids and synapsids. Some tetrapods such as snakes, legless lizards, and caecilians had evolved to become limbless via mutations of the Hox gene, although some do still have a pair of vestigial spurs that are remnants of the hindlimbs.

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<span class="mw-page-title-main">Jenny Clack</span> English paleontologist and evolutionary biologist (1947–2020)

Jennifer Alice Clack, was an English palaeontologist and evolutionary biologist. She specialised in the early evolution of tetrapods, specifically studying the "fish to tetrapod" transition: the origin, evolutionary development and radiation of early tetrapods and their relatives among the lobe-finned fishes. She is best known for her book Gaining Ground: the Origin and Early Evolution of Tetrapods, published in 2002 and written with the layperson in mind.

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Tulerpeton is an extinct genus of Devonian four-limbed vertebrate, known from a fossil that was found in the Tula Region of Russia at a site named Andreyevka. This genus and the closely related Acanthostega and Ichthyostega represent the earliest tetrapods.

<i>Eusthenodon</i> Extinct genus of tetrapodomorphs

Eusthenodon is an extinct genus of tristichopterid tetrapodomorphs from the Late Devonian period, ranging between 383 and 359 million years ago. They are well known for being a cosmopolitan genus with remains being recovered from East Greenland, Australia, Central Russia, South Africa, Pennsylvania, and Belgium. Compared to the other closely related genera of the Tristichopteridae clade, Eusthenodon was one of the largest lobe-finned fishes and among the most derived tristichopterids alongside its close relatives Cabonnichthys and Mandageria.

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<span class="mw-page-title-main">Stegocephali</span> Clade of tetrapodomorphs

Stegocephali is a clade of vertebrate animals containing all fully limbed tetrapodomorphs. It is equivalent to a broad definition of the superclass Tetrapoda: under this broad definition, the term "tetrapod" applies to any animal descended from the first vertebrate with four limbs each with five digits in the extremity (pentadactyly), rather than fins of their sarcopterygian relatives.

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<span class="mw-page-title-main">Ichthyostegalia</span> Paraphyletic group of tetrapodomorphs

Ichthyostegalia is an order of extinct amphibians, representing the earliest landliving vertebrates. The group is thus an evolutionary grade rather than a clade. While the group are recognized as having feet rather than fins, most, if not all, had internal gills in adulthood and lived primarily as shallow water fish and spent minimal time on land.

<i>Whatcheeria</i> Extinct genus of tetrapods

Whatcheeria is an extinct genus of early tetrapod from the Mississippian of Iowa. Fossils have been found in 340 million year old fissure fill deposits in the town of Delta. The type species, Whatcheeria deltae was named in 1995. It is classified within the family Whatcheeriidae, along with the closely related Pederpes and possibly Ossinodus.

<i>Ymeria</i> Extinct genus of tetrapodomorphs

Ymeria is an extinct genus of early stem tetrapod from the Devonian of Greenland. Of the two other genera of stem tetrapods from Greenland, Acanthostega and Ichthyostega, Ymeria is most closely related to Ichthyostega, though the single known specimen is smaller, the skull about 10 cm in length. A single interclavicle resembles that of Ichthyostega, an indication Ymeria may have resembled this genus in the post-cranial skeleton.

<i>Occidens portlocki</i> Extinct species of tetrapodomorph

Occidens is an extinct genus of stem tetrapod from the Early Carboniferous (Tournaisian) Altagoan Formation of Northern Ireland. It is known from a single type species, Occidens portlocki, named in 2004 on the basis of a left lower jaw described by British geologist Joseph Ellison Portlock in 1843.


Innovations conventionally associated with terrestrially first appeared in aquatic elpistostegalians such as Panderichthys rhombolepis, Elpistostege watsoni, and Tiktaalik roseae. Phylogenetic analyses distribute the features that developed along the tetrapod stem and display a stepwise process of character acquisition, rather than abrupt. The complete transition occurred over a period of 30 million years beginning with the tetrapodomorph diversification in the Middle Devonian.

References

  1. 1 2 Ahlberg, Per E.; Clack, Jennifer A. (2020). "The smallest known Devonian tetrapod shows unexpectedly derived features". Royal Society Open Science. 7 (4): 192117. Bibcode:2020RSOS....792117A. doi:10.1098/rsos.192117. PMC   7211834 . PMID   32431888.