Lutungutali

Lutungutali (meaning "high hip" in the Bemba language) is an extinct genus of silesaurid dinosauriform from the Middle Triassic of Zambia. The single type species of the genus is Lutungutali sitwensis. Lutungutali was named in 2013 and described from a fossil specimen, holotype NHCC LB32, including hip bones and tail vertebrae. The specimen was collected in 2009 from the upper Ntawere Formation, which dates to the Anisian stage of the Middle Triassic. Lutungutali is the first known silesaurid from Zambia and, along with the Tanzanian silesaurid Asilisaurus and dinosauriform Nyasasaurus, the oldest bird-line archosaur known from body fossils (i.e. parts of the skeleton).[1]

Lutungutali
Temporal range: Middle Triassic
Lutungutali
Holotype ilium with a scale bar
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dracohors
Clade: Silesauridae
Genus: Lutungutali
Peecook et al., 2013
Type species
Lutungutali sitwensis
Peecook et al., 2013

Description

Lutungutali is known from parts of its pelvis and from four caudal vertebrae that make up the base of the tail. These bones represent one individual, although bones that may belong to Lutungutali representing eight other individuals were collected from the same fossil site in 2011. Lutungutali shares the following three features (synapomorphies) with other early dinosauriforms:

  • A small area over which the pubis and ischium bones of the hip connect.
  • A depression or fossa on the ischium where it connects with the pubis and ilium.
  • The length of the ischium exceeding the length of the iliac blade across the top of the hip.

Lutungutali also shares two synapomorphies with the clade or evolutionary grouping containing silesaurids and dinosaurs:

  • A crest of bone extending upward from the supraacetabular crest (a bony ridge above the acetabulum or hip socket) that joins with the preacetabular process, the forward-most projection of the iliac blade.
  • A lengthy connection between the two pairs of ischia, except for a division of the two bones near their connection with the rest of the hip.

In addition, it shares two synapomorphies with other silesaurids:

  • A straight lower margin of the hip socket on the ilium (more basal dinosauriforms have a convex margin, and dinosaurs have a concave margin).
  • The lack of a ridge of bone behind the hip socket called the antitrochanter.

Lutungutali has one unique feature or autapomorphy that distinguishes it from all other dinosauriforms: an iliac blade that is taller than the portion of the ilium that forms the hip socket. This feature is references in its name, which means "high hip" in the Bemba Language.[1]

Phylogeny and evolutionary significance

Lutungutali belongs to Silesauridae, a family of archosaurs that is very closely related to Dinosauria. Silesaurids are known from southern Africa, Poland, the southwestern United States, and South America. When Lutungutali was named in 2013, a phylogenetic analysis (an analysis of evolutionary relationships) grouped it with the most derived silesaurids from the Late Triassic. The closest silesaurid in both space and time to Lutungutali is Asilisaurus from the Anisian-age Manda Beds of Tanzania, yet it was found to be a more basal silesaurid. Below is a cladogram from the analysis:[1]

Archosauria

Pseudosuchia

Avemetatarsalia

Pterosauromorpha

Lagerpetidae

Marasuchus

Silesauridae

Pseudolagosuchus/Lewisuchus

Asilisaurus

Lutungutali

Silesaurus

Sacisaurus

Eucoelophysis

Dinosauria

Lutungutali and Asilisaurus are the two oldest known members of Avemetatarsalia, the line of archosaurs that includes birds. The oldest known member of the other line of archosaurs, Pseudosuchia (crocodile-line archosaurs), is from the Olenekian stage of the Early Triassic, meaning that the first members of Avemetatarsalia must have appeared by this time. However, before the discovery of Asilisaurus (which was named in 2010), the oldest known avemetatarsalians were from the Ladinian stage of the Middle Triassic. Because Asilisaurus and Lutungutali are relatively derived members of Avemetatarsalia, their presence in the Anisian stage of the Middle Triassic suggests that avemetatarsalians underwent a rapid diversification at a time in their evolutionary history that was earlier than previously thought.[1]

References

  1. ^ a b c d Peecook, B. R.; Sidor, C. A.; Nesbitt, S. J.; Smith, R. M. H.; Steyer, J. S.; Angielczyk, K. D. (2013). "A new silesaurid from the upper Ntawere Formation of Zambia (Middle Triassic) demonstrates the rapid diversification of Silesauridae (Avemetatarsalia, Dinosauriformes)". Journal of Vertebrate Paleontology. 33 (5): 1127. doi:10.1080/02724634.2013.755991.
Averostra

Averostra, or "bird snouts", is a clade that includes most theropod dinosaurs that have a promaxillary fenestra (fenestra promaxillaris), an extra opening in the front outer side of the maxilla, the bone that makes up the upper jaw. Two groups of averostrans, the Ceratosauria and the Orionides, survived into the Cretaceous period. When the Cretaceous–Paleogene extinction event occurred, ceratosaurians and two groups of orionideans within the clade Coelurosauria, the Tyrannosauroidea and Maniraptoriformes, were still extant. Only one subgroup of maniraptoriformes, Aves, survived the extinction event and persisted to the present day.

Avetheropoda

Avetheropoda, or "bird theropods", is a clade that includes carnosaurians and coelurosaurs to the exclusion of other dinosaurs.

Cerapoda

Cerapoda ("ceratopsians and ornithopods") is a clade of the dinosaur order Ornithischia.

Dinosauriformes

Dinosauriformes is a clade of archosaurian reptiles that include the dinosaurs and their most immediate relatives. All dinosauriformes are distinguished by several features, such as shortened forelimbs and a partially to fully perforated acetabulum, the hole in the hip socket traditionally used to define dinosaurs. The oldest known member is Asilisaurus, dating to about 245 million years ago in the Anisian age of the middle Triassic period.

Haya griva

Haya is an extinct genus of basal neornithischian dinosaur known from Mongolia.

Jeholosauridae

Jeholosaurids were herbivorous neornithischian dinosaurs from the Cretaceous Period (Aptian - Santonian, with a possible Campanian record) of Asia. The family was first proposed by Han et al. in 2012. The jeholosaurids were defined as those ornithischians more closely related to Jeholosaurus shangyuanensis than to Hypsilophodon foxii, Iguanodon bernissartensis, Protoceratops andrewsi, Pachycephalosaurus wyomingensis, or Thescelosaurus neglectus. The Jeholosauridae includes the type genus Jeholosaurus and Yueosaurus.

Jingshanosaurus

Jingshanosaurus (meaning "Jingshan lizard") is a genus of sauropodomorph dinosaurs from the early Jurassic period.

Melanorosauridae

The Melanorosauridae were a family of sauropodomorph dinosaurs which lived during the Late Triassic and Early Jurassic. The name Melanorosauridae was first coined by Friedrich von Huene in 1929. Huene assigned several families of dinosaurs to the infraorder "Prosauropoda": the Anchisauridae, the Plateosauridae, the Thecodontosauridae, and the Melanorosauridae. Since then, these families have undergone numerous revisions. Galton and Upchurch (2004) considered Camelotia, Lessemsaurus, and Melanorosaurus members of the family Melanorosauridae. A more recent study by Yates (2007) indicates that the melanorosaurids were instead early sauropods.

Neotheropoda

Neotheropoda (meaning "new theropods") is a clade that includes coelophysoids and more advanced theropod dinosaurs, and the only group of theropods who survived the Triassic–Jurassic extinction event. Yet all of the neotheropods became extinct during the early Jurassic period except for Averostra.

Orionides

Orionides is a clade of tetanuran theropod dinosaurs from the Middle Jurassic to the Present. The clade includes most theropod dinosaurs, including birds.

Orodrominae

Orodrominae is a subfamily of parksosaurid dinosaurs from the Cretaceous of North America and Asia.

Powellvenator

Powellvenator is an extinct genus of coelophysoid theropod dinosaur that lived during the latter part of the Triassic Period in what is now northwestern Argentina. Fossils of the dinosaur were found in the Los Colorados Formation of the Ischigualasto-Villa Unión Basin. The type species, Powellvenator podocitus, was named by Martin Ezcurra in 2017.

Raeticodactylidae

Raeticodactylidae is a family of eudimorphodontoid eopterosaurian pterosaurs that lived in Switzerland during the Late Triassic. The family includes Caviramus, and the type genus Raeticodactylus, which are both known from the Kössen Formation, around 205 mya. Raeticodactylidae was first used in 2014 by Andres et al., as a group of all pterosaurs closer to Raeticodactylus than Eudimorphodon. The following phylogenetic analysis follows the topology of Andres et al. (2014).

Riojasauridae

Riojasauridae is a family of sauropod-like dinosaurs from the Upper Triassic. It is known primarily from the genera Riojasaurus and Eucnemesaurus. Sites containing Riojasauridae include the Lower Elliot Formation of Orange Free State, South Africa (where fossils of Eucnemesaurus have been found), and Ischigualasto, in La Rioja Province, Argentina ( where fossils of Riojasaurus have been recovered).

Silesauridae

Silesauridae is an extinct clade of Triassic dinosauriformes consisting of the closest known relatives of dinosaurs. As indicated by coprolite contents, some silesaurids such as Silesaurus may have been insectivorous, feeding selectively on small beetles and other arthropods.

Thescelosaurinae

Thescelosaurinae is a subfamily of ornithischian dinosaurs from the Early Cretaceous of Asia and the Late Cretaceous of North America.

Unaysauridae

Unaysauridae is a family of basal sauropodomorphs from the Late Triassic of India and Brazil.

Xixiposaurus

Xixiposaurus is a genus of prosauropod dinosaur which existed in what is now Lower Lufeng Formation, China during the lower Jurassic period. It was first named by Sekiya Toru in 2010 and the type species is Xixiposaurus suni.

Yueosaurus

Yueosaurus is an extinct genus of basal ornithopod dinosaur known from Zhejiang Province, China.

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