Herrerasauridae is a

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other ...

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 ...

s, possibly basal to either theropods or even all of saurischians, or even their own branching from

dracohors 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 lag ...

, separate from dinosauria altogether. They are among the oldest known dinosaurs, first appearing in the fossil record around 233.23 million years ago (the

Carnian The Carnian (less commonly, Karnian) is the lowermost stage (stratigraphy), stage of the Upper Triassic series (stratigraphy), Series (or earliest age (geology), age of the Late Triassic Epoch (reference date), Epoch). It lasted from 237 to 227 m ...

stage 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 ...

), before becoming extinct by the end of the

stage. Herrerasaurids were relatively small-sized dinosaurs, normally no more than long, although the holotype specimen of "''Frenguellisaurus ischigualastensis"'' (nowadays considered a synonym of ''Herrerasaurus'' ''ischigualastensis'') is thought to have reached around 6 meters (20 ft) long. The best known representatives of this group are from

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...

(

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the List of South American countries by area, second-largest ...

), where they were first discovered in the 1930s in relation to ''Staurikosaurus'' and 1960s in relation to ''Herrerasaurus''. A nearly complete skeleton of '' Herrerasaurus ischigualastensis'' was discovered in the

Ischigualasto Formation The Ischigualasto Formation is a Late Triassic fossiliferous formation and Lagerstätte in the Ischigualasto-Villa Unión Basin of the southwestern La Rioja Province and northeastern San Juan Province in northwestern Argentina. The formation ...

San Juan San Juan, Spanish for Saint John, may refer to: Places Argentina * San Juan Province, Argentina * San Juan, Argentina, the capital of that province * San Juan, Salta, a village in Iruya, Salta Province * San Juan (Buenos Aires Underground), ...

, Argentina, in 1988. Less complete possible herrerasaurids have been found in

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...

, and they may have inhabited other continents as well. Herrerasaurid anatomy is unusual and specialized, and they are not considered to be ancestral to any later dinosaur group. They only superficially resemble theropods and often present a mixture of very primitive and derived traits. 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) that c ...

is only partly open, and there are only 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 ...

, the lowest number among dinosaurs. The pubic bone has a derived structure, being rotated somewhat posteriorly and folded to create a superficially tetanuran-like terminal expansion, especially prominent in ''H. ischigulastensis''. The hand is primitive in having five

metacarpal In human anatomy, the metacarpal bones or metacarpus form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist, which forms the connection to the forearm. The metacarpal bones ar ...

s and the third finger longer than the second, but resembles those of theropods in having only three long fingers, with curved claws. Herrerasaurids also have a hinged

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

, which is also found in theropods.

Classification

It is not clear where herrerasaurids lie on the early dinosaur evolutionary tree. They are possibly basal theropods or basal saurischians. Early researchers even proposed that they represented an early lineage of sauropodomorphs. Some analyses, such as Nesbitt ''et al.'' 2009, have found ''Herrerasaurus'' and its relatives in Herrerasauridae to be very basal theropods, while others (such as Ezcurra 2010) have found them to be basal to the clade Eusaurischia, that is, closer to the base of the saurischian tree than either theropods or sauropodomorphs, but not true members of either. The situation is further complicated by uncertainties in correlating the ages of late Triassic beds bearing land animals. Other proposed members of the

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...

have included ''

Sanjuansaurus ''Sanjuansaurus'' (" San Juan Province lizard") is a genus of herrerasaurid dinosaur from the Late Triassic (Carnian) Cancha de Bochas and La Peña Members of the Ischigualasto Formation of the Ischigualasto-Villa Unión Basin in northwester ...

'' from the Ischigualasto Formation of Argentina, ''

Staurikosaurus ''Staurikosaurus'' (Pronounced "STORE-ee-koh-SAWR-us", " Southern Cross lizard") is a genus of herrerasaurid dinosaur from the Late Triassic of Brazil, found in the Santa Maria Formation. Description Colbert (1970) described ''Staurikosa ...

'' and ''

Gnathovorax ''Gnathovorax'' is a genus of herrerasaurid saurischian dinosaur from the Santa Maria Formation in Rio Grande do Sul, Brazil. The type and only species is ''Gnathovorax cabreirai'', described by Pacheco ''et al.'' in 2019. The type specimen ...

'' from the Santa Maria Formation of southern Brazil, '' Chindesaurus'' from the

Petrified Forest Petrified wood, also known as petrified tree (from Ancient Greek meaning 'rock' or 'stone'; literally 'wood turned into stone'), is the name given to a special type of '' fossilized wood'', the fossilized remains of terrestrial vegetation. ...

(

Chinle Formation The Chinle Formation is an Upper Triassic continental geological formation of fluvial, lacustrine, and palustrine to eolian deposits spread across the U.S. states of Nevada, Utah, northern Arizona, western New Mexico, and western Colorado. In N ...

) of

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

, and possibly '' Caseosaurus'' from the

Dockum Formation The Dockum is a Late Triassic (approximately late Carnian through Rhaetian, or 223–200 Ma) geologic group found primarily on the Llano Estacado of western Texas and eastern New Mexico with minor exposures in southwestern Kansas, eastern C ...

Texas Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...

, although the relationships of the North American animals are not fully understood, and not all paleontologists agree. Grzegorz Niedźwiedzki, Stephen L. Brusatte ''et al.'' (2014) described a

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

an putative member of the group on the basis of

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 ...

age fossils discovered in

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It is divided into 16 administrative provinces called voivodeships, covering an area of . Poland has a population of over 38 million and is the fifth-most populou ...

. An unnamed herresaurid was reported from the Carnian Pebbly Arkose Formation in

Zimbabwe Zimbabwe (), officially the Republic of Zimbabwe, is a landlocked country located in Southeast Africa, between the Zambezi and Limpopo Rivers, bordered by South Africa to the south, Botswana to the south-west, Zambia to the north, and ...

by Griffin ''et al.'' (2022). Other possible basal saurischians include '' Alwalkeria'' from the Late Triassic Maleri Formation of southern

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area, the List of countries and dependencies by population, second-most populous ...

, and ''

Teyuwasu ''Staurikosaurus'' (Pronounced "STORE-ee-koh-SAWR-us", " Southern Cross lizard") is a genus of herrerasaurid dinosaur from the Late Triassic of Brazil, found in the Santa Maria Formation. Description Colbert (1970) described ''Staurikosa ...

'' (recently considered synonym of ''

''), known from very fragmentary remains from the Late Triassic of Brazil. The discovery of the Herrerasaurid ''

'' indicates that the family falls outside the

Theropoda 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 ...

and Sauropodomorpha in the cladistic analysis undertaken on the genus when it was described, but remains squarely within Saurischia as basal members of the order. An unnamed herrerasaurid from the

of Brazil was described and possibly belongs to a new morphotype of relatively large proportions, informally known as the "Big ''

Saturnalia Saturnalia is an ancient Roman festival and holiday in honour of the god Saturn, held on 17 December of the Julian calendar and later expanded with festivities through to 23 December. The holiday was celebrated with a sacrifice at the Temple ...

''". In the phylogenetic analysis within this study, herrerasaurids are recovered as non- eusaurischian saurischians.

Phylogeny

Fernando Novas (1992) defined Herrerasauridae as ''Herrerasaurus'', ''Staurikosaurus'', and their most recent common ancestor.

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 si ...

(1998) defined the group as the most inclusive clade including ''H. ischigualastensis'' but not '' Passer domesticus''. Langer (2004) provided first phylogenetic definition of a higher level

taxon In biology, a taxon ( back-formation from '' taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular n ...

, Herrerasauria, as ''Herrerasaurus'' but not ''

Liliensternus ''Liliensternus'' is an extinct genus of basal neotheropod dinosaur that lived approximately 210 million years ago during the latter part of the Triassic Period in what is now Germany. ''Liliensternus'' was a moderate-sized, bipedal, ground-dwe ...

'' or '' Plateosaurus''. According to current phylogenetic studies, all of these definitions describe the same clade. The first

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...

presented follows one proposed analysis by Novas ''et al.'' in May 2011. In this review, ''Herrerasaurus'' is found to be a basal saurischian, but not a theropod. The second cladogram is based on an analysis by Sues ''et al.'' in April 2011. This review classified ''Herrerasaurus'' as a basal theropod. A large phylogenetic analysis of early dinosaurs by Matthew Baron, David Norman and Paul Barrett (2017) found Herrerasauridae within the clade Saurischia, as the

sister group In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

to Sauropodomorpha. This was the result of the removal of

from Saurischia and its placement next to

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 ...

within the newly created clade Ornithoscelida. Baron & Williams (2018) found Herrerasauria (including '' Daemonosaurus'', '' Caseosaurus'' and '' Saltopus'') outside Dinosauria. A similar result was provided by the phylogenetic analysis by Cau, 2018: Novas et al., 2021 revised the fossil record of South American early dinosaurs and supported that Herrerasauria is part of Saurischia but diverging earlier than both Sauropodomorpha or

, and further corroborated with the hypothesis that '' Chindesaurus'', '' Daemonosaurus'' and '' Tawa'' are members of the clade.

Timeline of genera

ImageSize = width:1000px height:auto barincrement:15px PlotArea = left:10px bottom:50px top:10px right:10px Period = from:-251.9 till:-201 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:5 start:-251 ScaleMinor = unit:year increment:1 start:-251 TimeAxis = orientation:hor AlignBars = justify Colors = #legends id:CAR value:claret id:ANK value:rgb(0.4,0.3,0.196) id:HER value:teal id:HAD value:green id:OMN value:blue id:black value:black id:white value:white id:mesozoic value:rgb(0.54,0.54,0.258) id:triassic value:rgb(0.51,0.17,0.57) id:earlytriassic value:rgb(0.6,0.22,0.61) id:middletriassic value:rgb(0.73,0.53,0.71) id:latetriassic value:rgb(0.78,0.65,0.8) id:jurassic value:rgb(0.2,0.7,0.79) id:earlyjurassic value:rgb(0,0.69,0.89) id:middlejurassic value:rgb(0.52,0.81,0.91) id:latejurassic value:rgb(0.74,0.89,0.97) id:cretaceous value:rgb(0.5,0.78,0.31) id:earlycretaceous value:rgb(0.63,0.78,0.65) id:latecretaceous value:rgb(0.74,0.82,0.37) BarData= bar:eratop bar:space bar:periodtop bar:space bar:NAM1 bar:NAM4 bar:NAM3 bar:NAM2 bar:NAM5 bar:space bar:period bar:space bar:era PlotData= align:center textcolor:black fontsize:M mark:(line,black) width:25 shift:(7,-4) bar:periodtop from: -251.9 till: -251.2 color:earlytriassic text: Ind. from: -251.2 till: -247.2 color:earlytriassic text: Olenekian from: -247.2 till: -242 color:middletriassic text:

Anisian In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from million years ago until million years ago. The Anisian Age succeeds the Olenekian Age (part of the Lower Triassic ...

from: -242 till: -237 color:middletriassic text:

Ladinian The Ladinian is a stage and age in the Middle Triassic series or epoch. It spans the time between Ma and ~237 Ma (million years ago). The Ladinian was preceded by the Anisian and succeeded by the Carnian (part of the Upper or Late Triassic) ...

from: -237 till: -227 color:latetriassic text:

from: -227 till: -208.5 color:latetriassic text:

from: -208.5 till: -201.3 color:latetriassic text:

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 ...

from: -201.3 till: -201 color:earlyjurassic bar:eratop from: -251.9 till: -247.2 color:earlytriassic text:

Early Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which is ...

from: -247.2 till: -237 color:middletriassic text:

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma an ...

from: -237 till: -201.3 color:latetriassic text:

from: -201.3 till: -201 color:earlyjurassic PlotData= align:left fontsize:M mark:(line,white) width:5 anchor:till align:left color:middletriassic bar:NAM1 from:-233.43 till:-233.23 text:

color:middletriassic bar:NAM4 from:-233.43 till:-233.23 text:

color:middletriassic bar:NAM3 from:-231.6 till:-231.4 text:

color:middletriassic bar:NAM2 from:-231.4 till:-228.91 text:

Herrerasaurus ''Herrerasaurus'' is a genus of saurischian dinosaur from the Late Triassic period. This genus was one of the earliest dinosaurs from the fossil record. Its name means "Herrera's lizard", after the rancher who discovered the first specimen i ...

color:latetriassic bar:NAM5 from:-221.5 till:-212 text: Caseosaurus PlotData= align:center textcolor:black fontsize:M mark:(line,black) width:25 bar:period from: -251.9 till: -251.2 color:earlytriassic text: Ind. from: -251.2 till: -247.2 color:earlytriassic text: Olenekian from: -247.2 till: -242 color:middletriassic text:

from: -242 till: -237 color:middletriassic text:

from: -237 till: -227 color:latetriassic text:

from: -227 till: -208.5 color:latetriassic text:

from: -208.5 till: -201.3 color:latetriassic text:

from: -201.3 till: -201 color:earlyjurassic bar:era from: -251.9 till: -247.2 color:earlytriassic text:

from: -247.2 till: -237 color:middletriassic text:

from: -237 till: -201.3 color:latetriassic text:

from: -201.3 till: -201 color:earlyjurassic

References

{{Taxonbar, from=Q134186 Prehistoric dinosaur families Prehistoric saurischians Carnian first appearances Norian extinctions