''Alocodon'' is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of
ornithischia
Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek s ...
n
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 ...
known from multiple teeth from the
Middle or
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987.
In European lithostratigraphy, the name ...
. The taxon was first described in
1973 by
Richard A. Thulborn for an assemblage of teeth from the Pedrógão locality of
Portugal
Portugal, officially the Portuguese Republic ( pt, República Portuguesa, links=yes ), is a country whose mainland is located on the Iberian Peninsula of Southwestern Europe, and whose territory also includes the Atlantic archipelagos of ...
, distinguished by an enlarged central
denticle
A denticle is any small tooth-like or bristle-like structure. "Denticle" may refer to:
* Denticle (tooth feature), serrations on the teeth of dinosaurs, lizards, sharks, and mammals
* Dermal denticles or placoid scales, in cartilaginous fishes
* ...
on the teeth, with the name taken from the
Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
''alox'' and ''odon'' meaning 'furrow tooth'.
The type specimen, a single tooth, is stored in the
Museu Geológico do Instituto Geológico e Mineiro in
Lisbon
Lisbon (; pt, Lisboa ) is the capital and largest city of Portugal, with an estimated population of 544,851 within its administrative limits in an area of 100.05 km2. Grande Lisboa, Lisbon's urban area extends beyond the city's administr ...
, Portugal, formerly having been kept in the collections of the
Free University of Berlin
The Free University of Berlin (, often abbreviated as FU Berlin or simply FU) is a public research university in Berlin, Germany. It is consistently ranked among Germany's best universities, with particular strengths in political science and t ...
as IPFUB P X 1, and comes from an individual under in length.
Though it was originally described as having been found in an unnamed deposit in the Portuguese Leiria District of upper
Callovian
In the geologic timescale, the Callovian is an age and stage in the Middle Jurassic, lasting between 166.1 ± 4.0 Ma (million years ago) and 163.5 ± 4.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the ...
age,
it was identified as having come from the lower
Oxfordian Cabaços Formation.
Alongside the 158 isolated teeth from Portugal assigned to ''Alocodon'', some isolated teeth from the
Bathonian
In the geologic timescale the Bathonian is an age and stage of the Middle Jurassic. It lasted from approximately 168.3 Ma to around 166.1 Ma (million years ago). The Bathonian Age succeeds the Bajocian Age and precedes the Callovian Age.
Strat ...
Forest Marble
The Forest Marble is a geological formation in England. Part of the Great Oolite Group, it dates to the late Bathonian stage of the Middle Jurassic.Weishampel, David B; et al. (2004). "Dinosaur distribution (Middle Jurassic, Europe)." In: Weisha ...
and
Chipping Norton Formations of
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 b ...
have been assigned to as cf. ''Alocodon sp.'' based on similarity.
''Alocodon'' was originally referred to as a member of the
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 wo ...
family
Fabrosauridae
Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek ...
by Thulborn in 1973, closest to ''
Fabrosaurus
''Fabrosaurus'' ( ) is an extinct genus of ornithischian dinosaur that lived during the Early Jurassic during the Hettangian to Sinemurian stages 199 - 189 mya.Ginsburg, L., (1964), "Decouverte d’un Scelidosaurien (Dinosaure ornithischien) ...
'' but also related to ''
Echinodon
''Echinodon'' is a genus of heterodontosaurid dinosaur that lived during the earliest Cretaceous of southern England and possibly western France in the Berriasian epoch. The first specimens were jaw bones named ''Echinodon becklesii'' by Sir Ric ...
'' and ''
Trimucrodon''.
Peter M. Galton retained it in the family in
1978
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, though he noted that there were significant differences between ''Alocodon'' and ''Fabrosaurus'', and the Middle to Late Jurassic fabrosaurids ''Alocodon'', ''Trimucrodon'' and ''Echinodon'' were representative of three independent branches of the family, with ''
Nanosaurus
''Nanosaurus'' ("small or dwarf lizard") is the name given to a genus of neornithischian dinosaur that lived about 155 to 148 million years ago, during the Late Jurassic-age. Its fossils are known from the Morrison Formation of the south-weste ...
'' not preserving enough material to determine its relationships.
Galton then suggested in
1983 that ''Alocodon'' was related to ''
Othnielia
''Nanosaurus'' ("small or dwarf lizard") is the name given to a genus of neornithischian dinosaur that lived about 155 to 148 million years ago, during the Late Jurassic-age. Its fossils are known from the Morrison Formation of the south-wes ...
'', based on similarities of the teeth, placed within the ornithopod family
Hypsilophodontidae.
Given that the species was only represented by teeth, ''Alocodon'' was designated as a ''
nomen dubium
In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application.
Zoology
In case of a ''nomen dubium'' it may be impossible to determine whether a s ...
'' in
1990
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by
David B. Weishampel and
Lawrence M. Witmer, as an indeterminate member of
Ornithischia
Ornithischia () is an extinct order of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek s ...
outside Ornithopoda.
While a basal ornithischian position outside Ornithopoda was retained 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 ...
in
1991
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, it was considered a possibly valid taxon based on its broad central denticle.
José Ruiz-Omeñaca reclassified ''Alocodon'' in
1999, based on a reconsideration of features and classifications specified previously. Though it had similarities to ornithopod, Ruiz-Omeñaca instead placed it within
Thyreophora
Thyreophora ("shield bearers", often known simply as "armored dinosaurs") is a group of armored ornithischian dinosaurs that lived from the Early Jurassic until the end of the Cretaceous.
Thyreophorans are characterized by the presence of body ...
as an intermediate taxon, as the tooth crown was asymmetrical, with the cingulum on one side higher than the other, and no ridges present on the crown.
Weishampel, Witmer and colleague
David B. Norman followed their 1990 opinion on ''Alocodon'' in
2004, though they noted that further study could potentially support the validity of the taxon.
Features of the teeth identified by José I. Canudo and colleagues in 2004 instead supported a more specific position for ''Alocodon'', as a member of
Ankylosauria
Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short, powerful limbs. ...
. Canudo ''et al.'' based this assignment on the anatomy of the denticles and
cingulum of the crown.
A denticulate cingulum present in ''Alocodon'' was also identified as an ankylosaur feature, by Paul M. Barrett and colleagues in
2010
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, though more material was considered necessary to verify the importance of the feature.
''Alocodon'' was considered an ornithopod by Filippo M. Rotatori and colleagues in
2020
2020 was heavily defined by the COVID-19 pandemic, which led to global Social impact of the COVID-19 pandemic, social and Economic impact of the COVID-19 pandemic, economic disruption, mass cancellations and postponements of events, COVID- ...
.
Because of its incomplete nature, ''Alocodon'' has been excluded from phylogenetic analyses.
A diversity of fauna is known from the Praia de Pedrógão locality alongside ''Alocodon'', including the
pterosaur
Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 to ...
''
Rhamphorhynchus
''Rhamphorhynchus'' (, from Ancient Greek ''rhamphos'' meaning "beak" and ''rhynchus'' meaning "snout") is a genus of long-tailed pterosaurs in the Jurassic period. Less specialized than contemporary, short-tailed pterodactyloid pterosaurs such ...
'', fragments of the shell of a
turtle
Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked tu ...
, remains of ''
Goniopholis
''Goniopholis'' (meaning "angled scale") is an extinct genus of goniopholidid crocodyliform that lived in Europe and Africa during the Late Jurassic and Early Cretaceous. Being semi-aquatic it is very similar to modern crocodiles. It ranged from ...
'' and another intermediate
crocodilia
Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living ...
n, material from a
kuehneosaurid
Kuehneosauridae is an extinct family of small, lizard-like gliding diapsids known from the Triassic period of Europe and North America. They are distinguished from other diapsids by their 'wings' formed by elongated ribs. These allowed the anim ...
and another unnamed
lizard
Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...
, an unnamed
salamander
Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten ...
, and teeth from the
teleost
Teleostei (; Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts ), is, by far, the largest infraclass in the class Actinopterygii, the ray-finned fishes, containing 96% of all extant species of fish. Tel ...
fishes ''
Caturus
''Caturus'' (from el, κατω , 'down' and el, οὐρά 'tail') is an extinct genus of fishes in the family Caturidae in the order Amiiformes, related to modern bowfin. Fossils of this genus range from 200 to 109 mya. It has been suggested ...
'', ''
Lepidotes
''Lepidotes'' (from el, λεπιδωτός , 'covered with scales') (previously known as ''Lepidotus'') is an extinct genus of Mesozoic ray-finned fish. It has been considered a wastebasket taxon, characterised by "general features, such as thi ...
'' and ''
Proscinetes'', and two
hybodontid sharks
Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachimorp ...
: ''
Asteracanthus
''Asteracanthus'' (from el, ἀστήρ , 'star' and el, ἄκανθα , 'spine') is an extinct genus of hybodontiform, known from the Middle Jurassic (Bathonian) to the Early Cretaceous (Valanginian).
Description
Astercanthus was among the ...
'' and an unnamed small form. Footprints and teeth of a very large
theropod
Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...
also indicate their presence in the locality.
References
Ornithischian genera
Middle Jurassic dinosaurs of Europe
Jurassic Portugal
Fossils of Portugal
Lourinhã Formation
Fossil taxa described in 1975
Taxa named by Richard A. Thulborn
Nomina dubia
{{ornithischian-stub