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

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of dinosauriform that lived during the Late

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

. It contains only one species, the

type species In International_Code_of_Zoological_Nomenclature, 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 spe ...

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

maxilla In vertebrates, the maxilla (: maxillae ) 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. The two maxil ...

astragalus Astragalus may refer to: * ''Astragalus'' (plant), a large genus of herbs and small shrubs *Astragalus (bone) The talus (; Latin for ankle or ankle bone; : tali), talus bone, astragalus (), or ankle bone is one of the group of foot bones known ...

and

humerus The humerus (; : humeri) 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 (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

, which date variously from the

Norian The Norian is a division of the Triassic geological period, Period. It has the rank of an age (geology), age (geochronology) or stage (stratigraphy), stage (chronostratigraphy). It lasted from ~227.3 to Mya (unit), million years ago. It was prec ...

and

Rhaetian The Rhaetian is the latest age (geology), age of the Triassic period (geology), Period (in geochronology) or the uppermost stage (stratigraphy), stage of the Triassic system (stratigraphy), System (in chronostratigraphy). It was preceded by the N ...

stages of the

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

, 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 Triass ...

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� ...

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

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

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 of Avon,

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

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 Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

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 (; : acetabula), also called the cotyloid cavity, is a wikt:concave, concave surface of the pelvis. The femur head, head of the femur meets with the pelvis at the acetabulum, forming the Hip#Articulation, hip joint. Structure The ...

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

sacral vertebrae The sacrum (: sacra or sacrums), in human anatomy, is a triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30. The sacrum situates at the upper, back part of the pelvic cavity, ...

; 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, Argentina and India. Classification The exact makeup and classification of the Guaibasauridae remain uncertain ...

. More recently, ''Agnosphitys'' has been considered a silesaurid based on an as-yet-unpublished description of '' Asilisaurus''.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 carried out by Matthew Baron, David Norman and Paul Barrett (2017) recovered ''Agnosphitys'' as a member of the clade Silesauridae.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 Sauropodomorpha Silesauridae Norian life Rhaetian life Late Triassic dinosaurs of Europe Triassic England Fossils of England Fossil taxa described in 2002 Taxa named by Kevin Padian