Tawa Hallae
   HOME

TheInfoList



OR:

''Tawa'' (named after the
Hopi The Hopi are Native Americans who primarily live in northeastern Arizona. The majority are enrolled in the Hopi Tribe of Arizona and live on the Hopi Reservation in northeastern Arizona; however, some Hopi people are enrolled in the Colorado ...
word for the
Puebloan The Pueblo peoples are Native Americans in the Southwestern United States who share common agricultural, material, and religious practices. Among the currently inhabited Pueblos, Taos, San Ildefonso, Acoma, Zuni, and Hopi are some of the ...
sun god) 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 possible basal
theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...
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 ...
s from 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 ...
period. The fossil remains of ''Tawa hallae'', the
type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...
and only species were found in the Hayden Quarry of
Ghost Ranch Ghost Ranch is a retreat and education center in Rio Arriba County in north central New Mexico, United States. It is about 65 miles northwest of Santa Fe and 14 miles from Abiquiu, the nearest community. In the later 20th century, it was the ...
,
New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...
, US. Its discovery alongside the relatives of ''
Coelophysis ''Coelophysis'' ( Traditional English pronunciation of Latin, traditionally; or , as heard more commonly in recent decades) is a genus of coelophysid Theropoda, theropod dinosaur that lived Approximation, approximately 215 to 201.4 million y ...
''and ''
Herrerasaurus ''Herrerasaurus'' is likely a genus of saurischian dinosaur from the Late Triassic period. Measuring long and weighing around , this genus was one of the earliest dinosaurs from the fossil record. Its name means "Herrera's lizard", after the ...
'' supports the hypothesis that the earliest dinosaurs arose in
Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...
during the early
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 ...
period in what is now South America, and radiated from there around the globe. 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 ...
honours Ruth Hall, founder of the Ghost Ranch Museum of Paleontology.


Description

''Tawa'' was estimated to have been long as an adult, with a weight of . ''Tawa'' preserves characters that can be associated with different dinosaur taxa. Its skull morphology resembles that of coelophysoids and the ilium approximates that of a herrerasaurid. Like the coelophysoids, ''Tawa'' has a kink in its upper jaws, between the
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 ...
and the
premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammals h ...
. With respect to limb proportion, the
femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...
is very long compared to the
tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...
. A neck
vertebra Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...
l adaptation in ''Tawa'' supports the hypothesis that cervical air sacs antedate the origin of the Neotheropoda and may be ancestral for
saurischia Saurischia ( , meaning "reptile-hipped" from the Greek ' () meaning 'lizard' and ' () meaning 'hip joint') is one of the two basic divisions of dinosaurs (the other being Ornithischia), classified by their hip structure. Saurischia and Ornithi ...
ns, and also links the dinosaurs with the evolution of birds. Compared to earlier dinosaurs such as ''
Herrerasaurus ''Herrerasaurus'' is likely a genus of saurischian dinosaur from the Late Triassic period. Measuring long and weighing around , this genus was one of the earliest dinosaurs from the fossil record. Its name means "Herrera's lizard", after the ...
''and ''
Eoraptor ''Eoraptor'' () is a genus of small, lightly built, Basal (phylogenetics), basal sauropodomorpha, sauropodomorph dinosaur. One of the earliest-known dinosaurs and one of the earliest sauropodomorphs, it lived approximately 231 to 228 million yea ...
'', ''Tawa'' had a relatively slender build. A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism or group. According to Nesbitt et al. (2009) ''Tawa'' can be distinguished based on the following features: the prootic bones meet on the ventral midline of the endocranial cavity, the anterior tympanic recess is greatly enlarged on the anterior surface of the basioccipital and extends onto the prootic and the parabasisphenoid, a deep recess is present on posterodorsal base of the paroccipital process, a sharp ridge extending dorsoventrally on the middle of the posterior face of the basal tuber, an incomplete ligamental sulcus is present on the posterior side of the femoral head, a semicircular muscle scar/excavation is present on the posterior face of femoral head, a small semicircular excavation on posterior margin of medial posterior
condyle A condyle (;Entry "condyle"
in
of proximal
tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...
, a "step" is present on the ventral surface of the
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 ...
,
metatarsal The metatarsal bones or metatarsus (: metatarsi) are a group of five long bones in the midfoot, located between the tarsal bones (which form the heel and the ankle) and the phalanges ( toes). Lacking individual names, the metatarsal bones are ...
I is similar in length to the other metatarsals.


Discovery

Fossils now attributed to ''Tawa'' were first discovered in 2004. The
holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...
, a juvenile individual, cataloged GR 241, consists of a mostly complete, but disarticulated skull, forelimbs, a partial
vertebral Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...
column, hindlimbs, ribs, and
gastralia Gastralia (: gastralium) are dermal bones found in the ventral body wall of modern crocodilians and tuatara, and many prehistoric tetrapods. They are found between the sternum and pelvis, and do not articulate with the vertebrae. In these reptil ...
. The determination was made that this specimen is a juvenile based on the presence of an open braincase and unfused neurocentral sutures. Fossils of at least seven other individuals were also discovered at the site. One of these specimens, cataloged GR 242, is also nearly complete. An isolated femur, GR 244, suggests that adults were at least 30% larger than the juvenile holotype. GR 242 was assigned as a
paratype In zoology and botany, a paratype is a specimen of an organism that helps define what the scientific name of a species and other taxon actually represents, but it is not the holotype (and in botany is also neither an isotype (biology), isotype ...
for the genus along with specimens representing a femora, pelvis, and tail (GR 155); and cervical
vertebrae Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...
(GR 243). All of these specimens are from the Hayden Quarry, a site in
New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...
, which preserves many fossils of early dinosaurs and their close relatives. They were discovered in gray/green siltstone dating to 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 ...
stage of the
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 ...
period, about 215-213 million years ago. ''Tawa'' was formally described in 2009 by a group of six American researchers led by Sterling J. Nesbitt of the
American Museum of Natural History The American Museum of Natural History (AMNH) is a natural history museum on the Upper West Side of Manhattan in New York City. Located in Theodore Roosevelt Park, across the street from Central Park, the museum complex comprises 21 interconn ...
. At the time of publication in the journal ''
Science Science is a systematic discipline that builds and organises knowledge in the form of testable hypotheses and predictions about the universe. Modern science is typically divided into twoor threemajor branches: the natural sciences, which stu ...
'', Nesbitt was a postdoctoral researcher at the
University of Texas at Austin The University of Texas at Austin (UT Austin, UT, or Texas) is a public university, public research university in Austin, Texas, United States. Founded in 1883, it is the flagship institution of the University of Texas System. With 53,082 stud ...
's Jackson School of Geosciences. Based on the study of the overlapping material of '' Dromomeron romeri'' and ''Tawa'', S. Christopher Bennett proposed that the two taxa were conspecific, forming a single growth series with ''D. romeri'' being the juvenile and ''Tawa'' being the adult. However, noting prominent differences between their femora which cannot be attributed to variation with age, Rodrigo Müller rejected this proposal in 2017. He further noted that while ''D. romeri'' is known from juveniles only, it shares many traits in common with ''D. gigas'', which is known from mature specimens.


Classification

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 ...
is ''Tawa hallae'', which was described in 2009 by Nesbitt ''et al.'', and considered more basal than ''
Coelophysis ''Coelophysis'' ( Traditional English pronunciation of Latin, traditionally; or , as heard more commonly in recent decades) is a genus of coelophysid Theropoda, theropod dinosaur that lived Approximation, approximately 215 to 201.4 million y ...
'', an early theropod from the Late Triassic. In 2009, Mortimer cautioned that the analysis by Nesbitt ''et al.'' was limited because it failed to consider all the characters of the relevant dinosaurs treated by the old analysis (e.g. ''Guaibasaurus'','' Panphagia'', ''
Sinosaurus ''Sinosaurus'' (meaning "Chinese lizard") is an extinct genus of basal theropod dinosaur which lived during the Early Jurassic (Hettangian-Sinemurian). Fossils of the animal have been found in the Lufeng Formation, in the Yunnan Province of Chi ...
'', ''Dracovenator'', ''Lophostropheus'', etc.)DML: http://dml.cmnh.org/2009Dec/msg00122.html ''Tawa'' was however found to be more advanced than the earliest
theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...
dinosaurs, ''
Eoraptor ''Eoraptor'' () is a genus of small, lightly built, Basal (phylogenetics), basal sauropodomorpha, sauropodomorph dinosaur. One of the earliest-known dinosaurs and one of the earliest sauropodomorphs, it lived approximately 231 to 228 million yea ...
'' and ''
Herrerasaurus ''Herrerasaurus'' is likely a genus of saurischian dinosaur from the Late Triassic period. Measuring long and weighing around , this genus was one of the earliest dinosaurs from the fossil record. Its name means "Herrera's lizard", after the ...
'', and '' Staurikosaurus''. Sues ''et al.'' (2011) considered ''Tawa'' a derived early
theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...
. A cladistic analysis of ''Tawa'' and other early theropods indicate that the Coelophysoidea, a group of early dinosaurs, may be an artificial grouping because ''Tawa'' combines classic coelophysoid features with features which appear to be ancestral to the neotheropods. ''Tawa'' is believed to be the
sister taxon 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 ...
of
Neotheropoda Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodomo ...
, a group of carnivorous dinosaurs which largely bore only three functional digits on their feet. In 2011, Martinez and colleagues concluded that ''Tawa'' was the basalmost coelophysoid, while a second 2011 analysis by paleontologists Martin D. Ezcurra and Stephen L. Brusatte, as well as a follow-up analysis modified with additional data by You Hai-Lu and colleagues in 2014, found ''Tawa'' to be a primitive theropod. This position for ''Tawa'' was also recovered in the large analysis of early dinosaurs by Matthew Baron, David B. Norman and Paul Barrett in 2017. Cau (2018) and Novas ''et al''. (2021) considered ''Tawa'' a non- herrerasaurid herrerasaur, although the first study placed Herrerasauria outside Dinosauria and the second placed it in Saurischia.


Paleoecology

The Hayden Quarry at
Ghost Ranch Ghost Ranch is a retreat and education center in Rio Arriba County in north central New Mexico, United States. It is about 65 miles northwest of Santa Fe and 14 miles from Abiquiu, the nearest community. In the later 20th century, it was the ...
belongs to the lower portion of the Petrified Forest Member of the Chinle Formation in
New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...
. The discovery of ''Tawa'' alongside the relatives of ''
Coelophysis ''Coelophysis'' ( Traditional English pronunciation of Latin, traditionally; or , as heard more commonly in recent decades) is a genus of coelophysid Theropoda, theropod dinosaur that lived Approximation, approximately 215 to 201.4 million y ...
'' and '' Camposaurus'' supports the hypothesis that the earliest dinosaurs arose in
Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...
during the Late Triassic period in what is now South America, and radiated around the globe from there. Ghost Ranch was located close to the equator 200 million years ago, and had a warm, monsoon-like climate with heavy seasonal precipitation. Hayden Quarry, an excavation site at Ghost Ranch, has yielded a diverse collection of fossil material that included the first evidence of dinosaurs and less-advanced dinosauromorphs from the same time period. The discovery indicates that the two groups lived together during the early Triassic period 235 million years ago. ''Tawas paleoenvironment included various archosauriforms such as crocodylomorphs, "
rauisuchia "Rauisuchia" is a paraphyletic group of mostly large and carnivorous Triassic archosaurs. Rauisuchians are a category of archosaurs within a larger group called Pseudosuchia, which encompasses all archosaurs more closely related to crocodilians ...
ns", phytosaurs, and dinosauriforms like ''
Dromomeron ''Dromomeron'' (meaning "running femur") is a genus of Lagerpetidae, lagerpetid Avemetatarsalia, avemetatarsalian which lived around 220 to 211.9 ± 0.7 million years ago. The genus contains species known from Late Triassic-age rocks of the South ...
'', ''
Chindesaurus ''Chindesaurus'' ( ) is an extinct genus of basal saurischian dinosaur from the Late Triassic (213-210 million years ago) of the southwestern United States. It is known from a single species, ''C. bryansmalli'', based on a partial skeleton recov ...
'', '' Eucoelophysis,'' and possibly ''
Coelophysis ''Coelophysis'' ( Traditional English pronunciation of Latin, traditionally; or , as heard more commonly in recent decades) is a genus of coelophysid Theropoda, theropod dinosaur that lived Approximation, approximately 215 to 201.4 million y ...
''.Irmis et al. 2007 Based on their review of the early carnivorous dinosaur fauna from Ghost Ranch and the Ischigualasto Formation Nesbit et al. (2009) observed that each was descended from a separate lineage, and inferred that the "South American" protocontinent
Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...
was the ancestral range for basal dinosaurs. Nesbit et al. (2009) went on to note that dinosaurs left their ancestral range in
Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...
and 200 million years ago they dispersed across the adjoined continents of Pangea. Nesbit ''et al.'' (2009) noted that repeated flooding events collected vertebrate bones, carcasses, and plant material from the landscape surface, possibly in
hyperconcentrated flow A hyperconcentrated flow is a two-phase flowing mixture of water and sediment in a channel which has properties intermediate between fluvial flow and debris flow.Pierson, Thomas C. "Hyperconcentrated flow—transitional process between water flow an ...
s, and deposited them at what is now Hayden Quarry. It was observed that these flooding events were separated by intervals where there was standing water and weakly developed, poorly drained (hydromorphic) soil formation. The ''Tawa'' specimens were very well preserved which suggests that they were buried extremely soon after dying.


See also

* 2009 in paleontology


References


External links

*
National Science Foundation The U.S. National Science Foundation (NSF) is an Independent agencies of the United States government#Examples of independent agencies, independent agency of the Federal government of the United States, United States federal government that su ...
br>special report on ''Tawa hallae
{{Taxonbar, from=Q132888 Saurischia Dinosaur species Norian dinosaurs Chinle Formation Taxa named by Sterling Nesbitt Taxa named by Mark Norell Fossil taxa described in 2009 Dinosaurs of the United States