Ignavusaurus

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Ignavusaurus
Temporal range: Early Jurassic, Hettangian
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Ignavusaurus Restoration.jpg
Restoration of Ignavusaurus
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Sauropodomorpha
Clade: Massopoda
Genus: Ignavusaurus
Knoll, 2010
Species:
I. rachelis
Binomial name
Ignavusaurus rachelis
Knoll, 2010

Ignavusaurus is a genus of basal sauropodomorph dinosaur that lived during the Early Jurassic in what is now Lesotho. Its fossils were found in the Upper Elliot Formation which is probably Hettangian in age (around 200 million years ago). It was described on the basis of a partial, well preserved articulated skeleton. The type species, I. rachelis, was described in 2010 by Spanish palaeontologist F. Knoll.

Contents

Discovery

The holotype was discovered in southern Lesotho near Ha Ralekoala. The fossils were discovered in a mostly articulated state, although the skull was badly damaged, having broken into more than 120 fragments. An unpublished 2002 Ph.D. dissertation referred to the remains, but they were not formally described for several years, and the find remained unpublished. [1]

In 2010, the fossils were described by F. Knoll of the Museo Nacional de Ciencias Naturales-CSIC in Madrid as a new taxon, Ignavusaurus rachelis. The fossils were brought to the National Museum of Natural History in Paris, where they were provisionally catalogued as BM HR 20; the plan was to return the fossils to Lesotho upon the opening of the Lesotho National Museum. [1]

Etymology

The generic name Ignavusaurus is derived from the Latin word ignavus ("coward") and Ancient Greek sauros ("lizard"). It refers to the type locality – Ha Ralekoala, that literally means "The place of the father of the coward". The specific name of the type species, rachelis, honours Spanish palaeontologist Raquel López-Antoñanzas. [1]

Description

The holotype had a body length of about 1.5 metres (4.9 ft) and weighed about 22.5 kilograms (50 lb). Histological analysis of the humerus and femur indicates that BM HR 20 was fast-growing individual, maybe less than one year old, based on age determination studies. [1]

Like other early sauropodomorphs, Ignavusaurus had a long, slender neck and tail. It generally resembled Massospondylus and Melanorosaurus , two other sauropodomorphs from southern Africa, although the shape and position of the teeth, among other factors, led Knoll to conclude that the remains belong to a previously unknown genus. [1]

Classification

Ignavusaurus is a basal sauropodomorph, a member of the long-necked, herbivorous, saurischian dinosaurs. Although originally recovered as more primitive than Plateosauria by Knoll (2010), Yates et al. (2011) noted that some characters used to place Ignavusaurus outside Massopoda are reflective of juvenile status and instead are more similar to juvenile Massospondylus, considering Ignavusaurus probably synonymous with Massospondylus . [2] Meanwhile, a cladistic analysis presented by Apaldetti et al. (2011) found Ignavusaurus to be a valid genus which is most closely related to Sarahsaurus within Massopoda, somewhat agreeing with Yates et al. that Ignavusaurus is not as primitive as originally thought. [3] A cladistic analysis conducted by Chapelle and Choiniere (2018) in their paper updating knowledge of the skull of Massospondylus recovered Ignavusaurus along with Sarahsaurus in Massospondylidae, as did the cladistic analysis of Chapelle et al. (2019). [4] [5]

Related Research Articles

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Sauropodomorpha is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had long necks and tails, were quadrupedal, and became the largest animals to ever walk the Earth. The prosauropods, which preceded the sauropods, were smaller and were often able to walk on two legs. The sauropodomorphs were the dominant terrestrial herbivores throughout much of the Mesozoic Era, from their origins in the Late Triassic until their decline and extinction at the end of the Cretaceous.

<i>Melanorosaurus</i> Sauropodomorph dinosaur genus from the Late Triassic period

Melanorosaurus is a genus of basal sauropodomorph dinosaur that lived during the Late Triassic period. An omnivore from South Africa, it had a large body and sturdy limbs, suggesting it moved quadrupedally. Its limb bones were massive and heavy like the limb bones of true sauropods.

<i>Massospondylus</i> Sauropodomorph dinosaur genus from Early Jurassic South Africa and Botswana

Massospondylus was a genus of sauropodomorph dinosaur from the Early Jurassic. It was described by Sir Richard Owen in 1854 from remains discovered in South Africa, and is thus one of the first dinosaurs to have been named. Fossils have since been found at other locations in South Africa, Lesotho, and Zimbabwe. Material from Arizona's Kayenta Formation, India, and Argentina has been assigned to the genus at various times, but the Arizonan and Argentinian material are now assigned to other genera.

<i>Antetonitrus</i> Sauropodiform dinosaur genus from Early Jurassic South Africa

Antetonitrus is a genus of sauropodiform dinosaur found in the Early Jurassic Elliot Formation of South Africa. The only species is Antetonitrus ingenipes. Sometimes considered a basal sauropod, it is crucial for the understanding of the origin and early evolution of this group. It was a quadrupedal herbivore, like its later relatives, but shows primitive adaptations to use the forelimbs for grasping, instead of purely for weight support.

<i>Blikanasaurus</i> Extinct genus of dinosaur from the late Triassic of South Africa

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<i>Euskelosaurus</i> Extinct genus of dinosaur from late Triassic southern Africa

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

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<i>Gryponyx</i> Extinct genus of dinosaur from early Jurassic South Africa

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

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

Massopoda is a clade of sauropodomorph dinosaurs which lived during the Late Triassic to Late Cretaceous epochs. It was named by paleontologist Adam M. Yates of the University of the Witwatersrand in 2007. Massopoda is a stem-based taxon, defined as all animals more closely related to Saltasaurus loricatus than to Plateosaurus engelhardti. Sauropodiformes is a more exclusive stem-based clade within Massopoda, defined as "the most inclusive clade containing Saltasaurus but not Massospondylus".

<span class="mw-page-title-main">Elliot Formation</span> Lithostratigraphic layer of the Stormberg Group in South Africa

The Elliot Formation is a geological formation and forms part of the Stormberg Group, the uppermost geological group that comprises the greater Karoo Supergroup. Outcrops of the Elliot Formation have been found in the northern Eastern Cape, southern Free State, and in the eastern KwaZulu-Natal provinces of South Africa. Outcrops and exposures are also found in several localities in Lesotho such as Qacha's Neck, Hill Top, Quthing, and near the capital, Maseru. The Elliot Formation is further divided into the lower (LEF) and upper (UEF) Elliot formations to differentiate significant sedimentological differences between these layers. The LEF is dominantly Late Triassic (Norian-Hettangian) in age while the UEF is mainly Early Jurassic (Sinemurian-Pliensbachian) and is tentatively regarded to preserve a continental record of the Triassic-Jurassic boundary in southern Africa. This geological formation is named after the town of Elliot in the Eastern Cape, and its stratotype locality is located on the Barkly Pass, 9 km north of the town.

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

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

Lessemsauridae is a clade of early sauropodiform dinosaurs that lived in the Triassic and Jurassic of Argentina, South Africa and possibly Lesotho. A phylogenetic analysis performed by Apaldetti and colleagues in 2018 recovered a new clade of sauropodiforms uniting Lessemsaurus, Antetonitrus, and Ingentia which they named Lessemsauridae. It is a node-based taxon, defined as all descendants of the most recent common ancestor of Lessemsaurus sauropoides and Antetonitrus ingenipes. Depending on the definition of Sauropoda, Lessemsauridae is either one of the most basal sauropod taxa, or a sister taxon of Sauropoda. An additional member of the clade was named later in 2018, Ledumahadi. A 2021 study by Pol and colleagues also assigned the genera Kholumolumo and Meroktenos to the group.

<i>Ngwevu</i> Sauropodomorph dinosaur genus from Early Jurassic South Africa

Ngwevu is a genus of massospondylid sauropodomorph dinosaur from the Lower Jurassic of South Africa. The genus contains one species, Ngwevu intloko.

References

  1. 1 2 3 4 5 Knoll, Fabien (2010). "A primitive sauropodomorph from the upper Elliot Formation of Lesotho". Geological Magazine. 147 (6): 814–829. Bibcode:2010GeoM..147..814K. doi:10.1017/S001675681000018X. S2CID   129174260. Archived from the original on 2012-03-13.
  2. Yates, Adam M.; Matthew F. Bonnan; Johann Neveling (2011). "A new basal sauropodomorph dinosaur from the Early Jurassic of South Africa". Journal of Vertebrate Paleontology. 31 (3): 610–625. doi:10.1080/02724634.2011.560626. S2CID   85589914.
  3. Cecilia Apaldetti; Ricardo N. Martinez; Oscar A. Alcober & Diego Pol (2011). Claessens, Leon (ed.). "A New Basal Sauropodomorph (Dinosauria: Saurischia) from Quebrada del Barro Formation (Marayes-El Carrizal Basin), Northwestern Argentina". PLOS ONE. 6 (11): e26964. Bibcode:2011PLoSO...626964A. doi: 10.1371/journal.pone.0026964 . PMC   3212523 . PMID   22096511.
  4. Chapelle KEJ, Choiniere JN. (2018) A revised cranial description of Massospondylus carinatus Owen (Dinosauria: Sauropodomorpha) based on computed tomographic scans and a review of cranial characters for basal Sauropodomorpha. PeerJ 6:e4224 https://doi.org/10.7717/peerj.4224
  5. Chapelle KEJ, Barrett PM, Botha J, Choiniere JN. 2019. Ngwevu intloko: a new early sauropodomorph dinosaur from the Lower Jurassic Elliot Formation of South Africa and comments on cranial ontogeny in Massospondylus carinatus. PeerJ 7:e7240 https://doi.org/10.7717/peerj.7240