''Stenopelix'' (meaning "narrow pelvis") 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 n ...

of small marginocephalian

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 ...

, possibly a basal

ceratopsia Ceratopsia or Ceratopia ( or ; Greek: "horned faces") is a group of herbivorous, beaked dinosaurs that thrived in what are now North America, Europe, and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurassi ...

n, from the

Early Cretaceous The Early Cretaceous (geochronological name) or the Lower Cretaceous ( chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pr ...

Germany Germany, officially the Federal Republic of Germany (FRG),, is a country in Central Europe. It is the most populous member state of the European Union. Germany lies between the Baltic and North Sea to the north and the Alps to the sou ...

. It lived in the late

Berriasian In the geological timescale, the Berriasian is an age/ stage of the Early/Lower Cretaceous. It is the oldest subdivision in the entire Cretaceous. It has been taken to span the time between 145.0 ± 4.0 Ma and 139.8 ± 3.0 Ma (million years a ...

Stage of the Cretaceous period, approximately 140 myr ago.Holtz, Thomas R. Jr. (2011) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,'
Winter 2010 Appendix.
/ref> The genus is based on a partial skeleton lacking the skull, and its classification is based on characteristics of the hips.

Discovery and species

In 1855, in a

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

quarry near

Bückeburg Bückeburg ( Northern Low Saxon: ''Bückeborg'') is a town in Lower Saxony, Germany, on the border with North Rhine Westphalia. It is located in the district of Schaumburg close to the northern slopes of the Weserbergland ridge. Population: 21 ...

on the Harrl, a fossil was found of a small dinosaur. Most of its bones were in a poor condition and removed on preparation, leaving two sets of hollow impressions on the plate and counterplate. The two plates do not overlap completely. The hollows, serving as a natural mold, have since been used to produce several casts in

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and dr ...

and

latex Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latexes are found in nature, but synthetic latexes are common as well. In nature, latex is found as a milky fluid found in 10% of all flowering plants (angiosper ...

to facilitate the study of the specimen. It was originally part of the collection of Max Ballerstedt preserved in the Bückeburg Gymnasium Adolfinum*Hermann Schmidt, 1969, "''Stenopelix valdensis'' H. v. Meyer, der kleine Dinosaurier des norddeutschen Wealden", ''Paläontologische Zeitschrift'' 43(3/4): 194-198 but was in 1976 moved to the Georg-August-Universität Göttingen where it now resides in the collection of the Geowissenschaftliches Zentrum der Universität Göttingen. In 1857, based on this fossil,

Christian Erich Hermann von Meyer Christian Erich Hermann von Meyer (3 September 1801 – 2 April 1869), known as Hermann von Meyer, was a German palaeontologist. He was awarded the 1858 Wollaston medal by the Geological Society of London. Life He was born at Frankfurt am M ...

named 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 specimen( ...

''Stenopelix valdensis''. The generic name is derived from Greek ''stenos'', "narrow", and ''pelyx'', "pelvis". The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

refers to the Wealden Formation. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...

, GZG 741/2 (earlier GPI 741-1, 2), found in the Obernkirchen Sandstein Formation, consists of the impressions of an almost complete skeleton, lacking the skull and the neck.

Description

''Stenopelix'' was a small herbivorous animal, reaching in length and in body mass. The preserved rump and tail have a combined length of just 97 centimetres; the femur is fourteen centimetres long. The species can be distinguished by several details of the pelvis. The shaft part of the

ilium Ilium or Ileum may refer to: Places and jurisdictions * Ilion (Asia Minor), former name of Troy * Ilium (Epirus), an ancient city in Epirus, Greece * Ilium, ancient name of Cestria (Epirus), an ancient city in Epirus, Greece * Ilium Building, a ...

uniformly tapers ending in a rounded point. The shaft of the

ischium The ischium () form ...

is thickest in the middle and there shows a distinctive kink.

Classification

The classification of ''Stenopelix'' is controversial and has ever been problematic because of the lacking skull. Prior to the 1960s, it was often assigned to some

ornithopod Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (), that started out as small, bipedal running grazers and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous worl ...

group. In 1974

Teresa Maryańska Teresa Maryańska (1937 – 3 October 2019) was a Polish paleontologist who specialized in Mongolian dinosaurs, particularly pachycephalosaurians and ankylosaurians. Peter Dodson (1998 p. 9) states that in 1974 Maryanska together with Hal ...

suggested it to be a pachycephalosaur, one of the oldest known, due to the apparent exclusion of the pubis from the

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) tha ...

, and the presence of strong caudal ribs. Peter Galton in 1982 showed that the "pubis" was actually part of the acetabulum, and the so-called "caudal ribs" were sacral ribs. The curvature of the

ischium The ischium () form ...

and absence of an

obturator foramen The obturator foramen (Latin foramen obturatum) is the large opening created by the ischium and pubis bones of the pelvis The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes ...

were not characteristics seen in other pachycephalosaurs. Galton concluded ''Stenopelix'' to be ceratopian. However, exact

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived ch ...

analyses by

Paul Sereno Paul Callistus Sereno (born October 11, 1957) is a professor of paleontology at the University of Chicago and a National Geographic "explorer-in-residence" who has discovered several new dinosaur species on several continents, including at sites ...

have resulted in a position in the

Pachycephalosauria Pachycephalosauria (; from Greek παχυκεφαλόσαυρος for 'thick headed lizards') is a clade of ornithischian dinosaurs. Along with Ceratopsia, it makes up the clade Marginocephalia. With the exception of two species, most pachycep ...

. But

paleontologists Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

Richard J. Butler Richard James Butler is a vertebrate palaeontologist at the University of Birmingham, where he holds the title of professor of palaeobiology. His research focuses on ornithischian dinosaur evolution, dinosaur origins, and fossil tetrapod macroevo ...

and

Robert M. Sullivan Robert Michael "Bob" Sullivan (born August 4, 1951) is a Vertebrate_paleontology, vertebrate paleontologist, noted for his work on fossil lizards and Dinosaur, dinosaurs. Sullivan discovered the second and most complete skull of the Hadrosaurid ...

nonetheless view the species as being Marginocephalia ''

incertae sedis ' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertain ...

'', rejecting the presumed

synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to hav ...

with the Pachycephalosauria as incorrect identifications or lacking cogency because of a possible presence in ceratopsian groups. In 2011, a

cladistic analysis Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived ch ...

performed by Butler ''et al.'' showed that ''Stenopelix'' is a basal member of the

Ceratopsia Ceratopsia or Ceratopia ( or ; Greek: "horned faces") is a group of herbivorous, beaked dinosaurs that thrived in what are now North America, Europe, and Asia, during the Cretaceous Period, although ancestral forms lived earlier, in the Jurassi ...

, and its sister taxon is ''

Yinlong ''Yinlong'' (, meaning "hidden dragon") is a genus of basal ceratopsian dinosaur from the Late Jurassic Period of central Asia. It was a small, primarily bipedal herbivore. Discovery and species A coalition of American and Chinese paleontologi ...

''. In 2020, Yu ''et al''. classified ''Stenopelix'' as a chaoyangsaurid with ''Yinlong'', '' Chaoyangsaurus,

Xuanhuaceratops ''Xuanhuaceratops'' (meaning "Xuanhua horned face") is a genus of dinosaur from the Late Jurassic Period. The genus was in 2006 dated to the Tithonian, 150.8-145.5 million years ago. A member of the family Chaoyangsauridae, it was one of the ear ...

, Hualianceratops.''

References

External links

Article about ''Stenopelix'' on ''DinosaurusBlog'' (in Czech)
{{Taxonbar, from=Q134600 Ceratopsians Marginocephalians Berriasian life Early Cretaceous dinosaurs of Europe Cretaceous Germany Fossils of Germany Fossil taxa described in 1857 Taxa named by Christian Erich Hermann von Meyer Ornithischian genera

Discovery and species

Description

Classification

See also

References

External links