''Agnosphitys'' (; "unknown begetter"; sometimes mistakenly called ''Agnostiphys'' or ''Agnosphytis'') is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

dinosauriform Dinosauromorpha is a clade of avemetatarsalian archosaurs (reptiles closer to birds than to crocodilians) that includes the Dinosauria (dinosaurs) and some of their close relatives. It was originally defined to include dinosauriforms and lage ...

that lived during the Late

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest per ...

. It contains only one species, the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specim ...

''A. cromhallensis''. Its remains include an ilium,

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. T ...

astragalus ''Astragalus'' is a large genus of over 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. It is the largest genus of plants in terms of described species. The genus is native to tempe ...

and

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a r ...

, which date variously from the

Norian The Norian is a division of the Triassic Period. It has the rank of an age ( geochronology) or stage (chronostratigraphy). It lasted from ~227 to million years ago. It was preceded by the Carnian and succeeded by the Rhaetian. Stratigraphic ...

and

Rhaetian The Rhaetian is the latest age of the Triassic Period (in geochronology) or the uppermost stage of the Triassic System (in chronostratigraphy). It was preceded by the Norian and succeeded by the Hettangian (the lowermost stage or earliest a ...

stages of the

Late Triassic The Late Triassic is the third and final epoch of the Triassic Period in the geologic time scale, spanning the time between Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch and followed by the Early Jurassic Epoch ...

, or possibly as late as the

Hettangian The Hettangian is the earliest age and lowest stage of the Jurassic Period of the geologic timescale. It spans the time between 201.3 ± 0.2 Ma and 199.3 ± 0.3 Ma (million years ago). The Hettangian follows the Rhaetian (part of the Triassi ...

stage of the

Early Jurassic The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...

. The fissure fill at Avon, of which ''Agnosphitys'' was probably recovered from, was a sinkhole formed by the dissolution of

Lower Carboniferous Lower may refer to: *Lower (surname) *Lower Township, New Jersey *Lower Receiver (firearms) *Lower Wick Gloucestershire, England See also *Nizhny Nizhny (russian: Ни́жний; masculine), Nizhnyaya (; feminine), or Nizhneye (russian: Ни́� ...

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms w ...

Discovery and naming

The type species, ''Agnosphitys cromhallensis'', was described by Nicholas Fraser, Kevin Padian, Gordon Walkden and A. L. M Davis in early 2002. The fossils consist of two specimens. The holotype consists of a single isolated left ilium, while the second specimen consists of a partial skeleton including a left maxilla, a humerus and a left

, were found in the

Magnesian Conglomerate The Magnesian Conglomerate is a geological formation in Clifton, Bristol in England (originally Avon), Gloucestershire and southern Wales, present in Tytherington, Durdham Down and Cromhall Quarry. It dates back to the Rhaetian stage of the Lat ...

of Avon,

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe ...

Classification

The remains of ''Agnosphitys'' defied precise classification in the original description; the describers placed it outside

Dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

ia using the definition of Dinosauria outlined by Padian and May (1995) and provided (on p. 80) the following diagnosis: "Well-defined brevis fossa on the ilium; semi-perforate

acetabulum The acetabulum (), also called the cotyloid cavity, is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint. Structure There are three bones of the ''os coxae'' (hip bone) that c ...

; `kidney-shaped' antitrochanter; well-developed posterior portion of the iliac blade; two

sacral vertebrae The sacrum (plural: ''sacra'' or ''sacrums''), in human body, human anatomy, is a large, triangular bone at the base of the vertebral column, spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30. The sacrum situ ...

; subrectangular deltopectoral crest that is 33 per cent of the length of the humerus; astragalus with a distinct ascending process and a prominent depression immediately posterior to the ascending process; in dorsal aspect an acute anteromedial corner on the astragalus."Nicholas C. Fraser, Kevin Padian, Gordon M. Walkden and A. L. M. Davis, 2002. Basal dinosauriform remains from Britain and the diagnosis of the Dinosauria. Palaeontology. 45(1), 79-95. Despite the paucity of known fossils, ''Agnosphitys'' has been included in two phylogenetic analyses analyzing primitive dinosaur relationships. Yates (2007) recovered the genus as a theropod, whereas Ezcurra (2010) recovered it as a member of

Guaibasauridae Guaibasauridae is a family of basal sauropodomorph dinosaurs, known from fossil remains of late Triassic period formations in Brazil and Argentina. Classification The exact makeup and classification of the Guaibasauridae remain uncertain. The ...

. More recently, ''Agnosphitys'' has been considered a silesaurid based on an as-yet-unpublished description of ''

Asilisaurus ''Asilisaurus'' ( ); from Swahili, ''asili'' ("ancestor" or "foundation"), and Greek, (, "lizard") is an extinct genus of silesaurid archosaur. The type species is ''Asilisaurus kongwe.'' ''Asilisaurus'' fossils were uncovered in the Manda Bed ...

''.Nesbitt, Sidor, Irmis, Stocker, Angielczyk, and Smith, 2015. THE ANATOMY OF ''ASILISAURUS KONGWE'' (DINOSAURIFORMES: SILESAURIDAE) AND CLOSELY-RELATED TAXA PROVIDES NEW INSIGHTS INTO THE ANATOMICAL AND CHRONOLOGICAL EVOLUTION OF DINOSAURIFORMS. Journal of Vertebrate Paleontology 35 (Supplement):187A-188A. A large phylogenetic analysis of early dinosaurs and

dinosauromorphs Dinosauromorpha is a clade of avemetatarsalian archosaurs (reptiles closer to birds than to crocodilians) that includes the Dinosauria (dinosaurs) and some of their close relatives. It was originally defined to include dinosauriforms and lage ...

carried out by Matthew Baron, David Norman and Paul Barrett (2017) recovered ''Agnosphitys'' as a member of the clade

Silesauridae Silesauridae is an extinct family of Triassic dinosauriforms. It is most commonly considered to be a clade of non-dinosaur dinosauriforms, and the sister group of dinosaurs. Some studies have instead suggested that most or all silesaurids compri ...

.Baron, M.G., Norman, D.B., and Barrett, P.M. (2017). A new hypothesis of dinosaur relationships and early dinosaur evolution. ''Nature'', 543: 501–506.

References

{{Taxonbar, from=Q134614 Sauropodomorphs Silesaurids Norian life Rhaetian life Late Triassic dinosaurs of Europe Triassic England Fossils of England Fossil taxa described in 2002 Taxa named by Kevin Padian