Nhandumirim
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''Nhandumirim'' (meaning "small rhea" in the
Tupi language Old Tupi, Ancient Tupi or Classical Tupi () is a classical Tupian language which was spoken by the indigenous Tupi people of Brazil, mostly those who inhabited coastal regions in South and Southeast Brazil. In the words of Brazilian tupinol ...
) 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 basal
sauropodomorph Sauropodomorpha ( ; from Greek, meaning "lizard-footed forms") is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had lo ...
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 ...
from 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 227.3 ...
age of
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 ...
Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...
. It is currently considered a saturnaliid sauropodomorph. 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, ''Nhandumirim waldsangae'', is known from a single immature specimen including
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 ...
e, a , pelvic material, and a hindlimb found in the
Santa Maria Formation The Santa Maria Formation is a sedimentary rock formation found in Rio Grande do Sul, Brazil. It is primarily Carnian in age (Late Triassic), and is notable for its fossils of cynodonts, " rauisuchian" pseudosuchians, and early dinosaurs and othe ...
in
Rio Grande do Sul Rio Grande do Sul (, ; ; "Great River of the South") is a Federative units of Brazil, state in the South Region, Brazil, southern region of Brazil. It is the Federative units of Brazil#List, fifth-most populous state and the List of Brazilian s ...
. ''Nhandumirim'' is differentiated from other Santa Maria dinosaurs such as ''
Staurikosaurus ''Staurikosaurus'' (Pronounced /ˌstɔɹ̠ikoʊˈsɔɹ̠ʌs/, '' STOR-ree-koh-SOR-ruhs''; "Southern Cross lizard") is a genus of herrerasaurid dinosaur from the Late Triassic of Brazil, found in the Santa Maria Formation. Description Colber ...
'' and ''
Saturnalia Saturnalia is an Roman festivals, ancient Roman festival and holiday in honour of the List of Roman deities, god Saturn (mythology), Saturn, held on 17 December in the Julian calendar and later expanded with festivities until 19 December. By t ...
'' on the basis of its more gracile, long-legged proportions and several more specific skeletal features. However, it is noteworthy that the holotype of ''Nhandumirim'' is an immature individual. Several features of 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 ...
led the describers of the genus and species to consider ''Nhandumirim'' ''waldsangae'' possibly 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 ...
, but some analyses in their study offer alternative positions within
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 ...
. All subsequent studies considered ''Nhandumirim'' an early
sauropodomorph Sauropodomorpha ( ; from Greek, meaning "lizard-footed forms") is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had lo ...
, closely-associated with ''
Saturnalia Saturnalia is an Roman festivals, ancient Roman festival and holiday in honour of the List of Roman deities, god Saturn (mythology), Saturn, held on 17 December in the Julian calendar and later expanded with festivities until 19 December. By t ...
'' and '' Chromogisaurus''.


Discovery

''Nhandumirim'' is known from a single partial skeleton, LPRP/ USP 0651, which includes several vertebrae, a right ilium, and most of a right hindlimb. This skeleton was found at the site of Cerro da Alemoa (also known as Waldsanga or Sanga do Mato) in
Santa Maria, Rio Grande do Sul Santa Maria is a municipality (''município'') in the central region of Rio Grande do Sul, the southernmost state of Brazil. In 2020, its population was 283,677 inhabitants in a total area of . Santa Maria is the 5th biggest municipality in the ...
. Waldsanga is a historically important Triassic site which also preserved the
type specimens In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to anchor or centralizes t ...
of ''
Saturnalia Saturnalia is an Roman festivals, ancient Roman festival and holiday in honour of the List of Roman deities, god Saturn (mythology), Saturn, held on 17 December in the Julian calendar and later expanded with festivities until 19 December. By t ...
'', ''
Rauisuchus ''Rauisuchus'' (meaning "Wilhelm Rau's crocodile") is a genus of extinct archosaurs which lived in what is now the Geopark of Paleorrota (Santa María Formation), Brazil, during the Triassic, Late Triassic period (235–228 million years ago). It ...
'', ''
Gomphodontosuchus ''Gomphodontosuchus'' is an extinct genus of cynodonts. It was created to describe the species ''Gomphodontosuchus brasiliensis''. Species ''Gomphodontosuchus brasiliensis'' was collected in 1927 and named in 1928 by Friedrich von Huene in the S ...
'', and ''
Alemoatherium ''Alemoatherium'' is an extinct genus of prozostrodontian cynodont which lived in the Late Triassic of Brazil. It contains a single species, ''A. huebneri'', named in 2017 by Agustín Martinelli and colleagues. The genus is based on UFSM 11579b, ...
''. The site preserves Carnian-age sediments of the
Santa Maria Formation The Santa Maria Formation is a sedimentary rock formation found in Rio Grande do Sul, Brazil. It is primarily Carnian in age (Late Triassic), and is notable for its fossils of cynodonts, " rauisuchian" pseudosuchians, and early dinosaurs and othe ...
, and LPRP/USP 0651 specifically comes from the top of the Alemoa member on that site. The generic name ''Nhandumirim'' roughly translates to "small rhea" in the Tupi-Guarani language. 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 Waldsanga.


Description

The
dorsal vertebrae In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebra (anatomy), vertebrae of intermediate size between the ce ...
have spool-shaped
centra Centra is a convenience shop chain that operates throughout Ireland. The chain operates as a symbol group owned by Musgrave Group, the food wholesaler, meaning the individual shops are all owned by individual franchisees. The chain has three ...
which are about 1.4 times longer than high, making them more elongated than those of herrerasaurids. Several areas on the dorsals are incised, such as the sides of the centrum (which each have a shallow depression) and the rear of the neural arch (which has postzygapophyseal centrodiapophyseal and centrodiapophyseal fossae). There were likely three
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, ...
, with at least the first one articulating with the hip akin to the "primordial" first sacral of other reptiles. This contrasts with ''
Saturnalia Saturnalia is an Roman festivals, ancient Roman festival and holiday in honour of the List of Roman deities, god Saturn (mythology), Saturn, held on 17 December in the Julian calendar and later expanded with festivities until 19 December. By t ...
'' in which the first sacral vertebra is an incorporated dorsal vertebra without the hallmarks of a primordial sacral. The sacral vertebrae were thick and wide, but not fused to each other or their respective sacral ribs. The most complete sacral rib was fan shaped when seen from above and has a cross section which gradually curves upwards towards the front, also unlike ''Saturnalia'' which has a more L-shaped cross section. The
caudal vertebrae Caudal vertebrae are the vertebrae of the tail in many vertebrates. In birds, the last few caudal vertebrae fuse into the pygostyle, and in apes, including humans, the caudal vertebrae are fused into the coccyx. In many reptiles, some of the caud ...
increase in length and gradually reduce the size of their
transverse processes 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 ...
from the base of the tail to the tip. Caudals at the base of the tail have pronounced midline keels along their entire lower edge. This characteristic is seemingly unique to ''Nhandumirim'', as the only other
dinosauromorphs Dinosauromorpha is a clade of avemetatarsalians (archosaurs 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 lagerpetids, ...
with ventral keels in proximal caudals are ''
Dracoraptor ''Dracoraptor'' (meaning "dragon thief") is a genus of coelophysoid dinosaur that lived during the Hettangian stage of the Early Jurassic Period of what is now Wales dated at 201.3 ± 0.2 million years old. The fossil was first discovered in 2 ...
'' (which had paired, not midline, keels) and ''
Efraasia ''Efraasia'' (pronounced "E-FRAHS-ee-A") is a genus of basal (phylogenetics), basal sauropodomorph dinosaur. It was a herbivore which lived during the middle Norian stage of the Late Triassic, around 210 million years ago, in what is now Germ ...
'' (in which they were restricted to the front third of the centrum). The zygapophyses of the caudals are short, unlike the longer joints of herrerasaurids and
neotheropods 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 Sauropodomor ...
. The ilium is generally typical for early dinosaurs, with a perforated acetabulum, conspicuous antitrochanter, and a postacetabular process which was much longer than the preacetabular process. The ischiadic peduncle is expanded in a front-to-back direction like that of neotheropods. There is an L-shaped scar on the inner edge of the iliac blade which received the first sacral vertebra, and there was enough room for two more sacrals behind it. The outer surface of postacetabular process has two holes and a pronounced incision along its lower edge, known as a brevis fossa. In most dinosaurs which have a brevis fossa, it clearly starts at the base of the postacetabular process, according to a ridge which delineates its upper edge. However, ''Nhandumirim'''s brevis fossa only occupies the rear 3/4ths of the postacetabular process, with no clear interaction with the main portion of the ilium. 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 slender and thin-walled. The proximal portion possessed early dinosaurian hallmarks such as an anterior trochanter, a facies articularis antitrochanterica, well-developed medial tubera separated by a deep ligament sulcus, and an asymmetrical and pronounced fourth trochanter. The femoral head also possessed a deep and curved groove, but the appearance of this groove is known to be variable within some dinosaur species, so it is not particularly informative for ''Nhandumirim'''s classification. The trochanteric shelf was not present, but a homologous muscle attachment scar did exist in the same area, along with a more proximally-located anterolateral scar similar to that reported in some
silesaurids Silesauridae is an extinct family of Triassic dinosauriforms. It is most commonly considered to be a clade of non-dinosaur dinosauriforms, and the sister group of dinosaurs. Some studies have instead suggested that most or all silesaurids compr ...
. Unlike other early dinosaurs, the dorsolateral trochanter was characteristically short, ending quite a distance away from the femoral head like the anterior trochanter. The distal portion had a wide medial condyle and muscle scars similar to those of ''Herrerasaurus''. 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 ...
was poorly preserved but did possess several features similar to those of neotheropods. These include a tall facet for the ascending process 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 ...
and a distal tip which was wide and flattened when seen from below and boxy when seen from the front. There was also a diagonal mound-like tuberosity on the anterior surface of the tibia. ''Nhandumirim'' is the only known dinosaur to possess both these neotheropod-like traits and a diagonal tuberosity. The more complete
fibula The fibula (: fibulae or fibulas) or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. ...
was elongated (~10% longer than the femur) and had scars for the tibial ligament and iliofibularis muscle near the knee. There was a semicircular facet for the ascending process of the astragalus on the portion of the fibula contacting the heel, a characteristic unique to ''Nhandumirim''. Metatarsal II is straight, with a flattened proximal portion and boxy distal portion. Metatarsal IV has a more irregularly-shaped distal portion but is also straight, an unusual feature more akin to ''
Lagerpeton ''Lagerpeton'' is a genus of lagerpetid avemetatarsalian, comprising a single species, ''L. chanarensis''. First described from the Chañares Formation of Argentina by A. S. Romer in 1971, ''Lagerpeton'' anatomy is somewhat incompletely k ...
'' and
pterosaur Pterosaurs are 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 million to 66 million years ago). Pterosaurs are the earli ...
s rather than the more curved bone of other dinosaurs. Isolated
phalanges The phalanges (: phalanx ) are digit (anatomy), digital bones in the hands and foot, feet of most vertebrates. In primates, the Thumb, thumbs and Hallux, big toes have two phalanges while the other Digit (anatomy), digits have three phalanges. ...
are variable in proportions, with one having a wide proximal articulation and the rest having tall, triangular proximal articulations and more well-developed joint surfaces.
Ungual An ungual (from Latin ''unguis'', i.e. ''nail'') is a highly modified distal toe bone which ends in a hoof, claw, or nail. Elephants and ungulates have ungual phalanges, as did the sauropod Sauropoda (), whose members are known as sauropods (; ...
s are triangular in cross section and curved, though not to the extent seen in more advanced theropods.


Classification

The describers of ''Nhandumirim'' tested its relations using two
phylogenetic analyses In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as Computational phylogenetics, phylogenetic inference. It infers the relationship among organ ...
focused around the origin of dinosaurs. The first one, created previously by
Cabreira La Cabrera (Cabreira in Leonese language) is a comarca (shire) in the province of León, Spain. Its surface is 115.87 km2 and the population was 4,227 inhabitants in 2007. The Sierra de la Cabrera range dominates the landscape of this mount ...
''et al.'' (2016), considered it the basalmost theropod, as 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 ...
to
neotheropods 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 Sauropodomor ...
. This is supported by a wide ischiadic peduncle and several traits of 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 ...
. The Cabreira ''et al.'' (2016) analysis is notable for excluding several other traditional basal theropods from the group. These include ''
Daemonosaurus ''Daemonosaurus'' is an extinct genus of possible theropod dinosaur from the Late Triassic of New Mexico. The only known fossil is a skull and neck fragments from deposits of the latest Triassic Chinle Formation at Ghost Ranch. ''Daemonosaurus'' ...
'', '' Tawa'', ''
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 ...
'', and ''
Eodromaeus ''Eodromaeus'' (meaning "dawn runner") is an extinct genus of probable basal (phylogenetics), basal theropod dinosaurs from the Late Triassic of Argentina. Like many other of the earliest-known dinosaurs, it hails from the Carnian-age (~230 Ma) I ...
'', which are considered basal
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 according to their results. Adding ''Nhandumirim'' to the second analysis, created by Nesbitt &
Ezcurra Ezcurra is a surname. Notable people with the surname include: * Alma Ezcurra (born 1986), Spanish politician * Bautista Ezcurra (born 1995), Argentine rugby union player * Encarnación Ezcurra (1795–1838), Argentine political activist * Exequiel ...
(2015), led to inconclusive results. In the strict consensus tree (average result of most parsimonious trees), ''Nhandumirim'' is part of a broad
polytomy An internal node of a phylogenetic tree is described as a polytomy or multifurcation if (i) it is in a rooted tree and is linked to three or more child subtrees or (ii) it is in an unrooted tree and is attached to four or more branches. A tree ...
at the base of
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 ...
, along with several traditional basal theropods, herrerasaurids, 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 ...
'' (which, on the other hand, is frequently considered an early sauropodomorph in most recent analyses). This is because it is a "wildcard" taxon with several equally likely positions within Saurischia. These positions may include ''Nhandumirim'' as the sister taxon to all other saurischians, as the sister taxon to ''Eoraptor'', or as the sister taxon to all other theropods (which also includes herrerasaurids in this option). Regardless, the authors considered unlikely that ''Nhandumirim'' is particularly close to ''
Staurikosaurus ''Staurikosaurus'' (Pronounced /ˌstɔɹ̠ikoʊˈsɔɹ̠ʌs/, '' STOR-ree-koh-SOR-ruhs''; "Southern Cross lizard") is a genus of herrerasaurid dinosaur from the Late Triassic of Brazil, found in the Santa Maria Formation. Description Colber ...
'' or ''
Saturnalia Saturnalia is an Roman festivals, ancient Roman festival and holiday in honour of the List of Roman deities, god Saturn (mythology), Saturn, held on 17 December in the Julian calendar and later expanded with festivities until 19 December. By t ...
''. Nonetheless, the phylogenetic position of ''Nhandumirim'' was also tested in the article describing ''
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 com ...
cabreirai'', which recovered it as a saturnaliine
sauropodomorph Sauropodomorpha ( ; from Greek, meaning "lizard-footed forms") is an extinct clade of long-necked, herbivorous, saurischian dinosaurs that includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had lo ...
, close-associated with ''
Saturnalia Saturnalia is an Roman festivals, ancient Roman festival and holiday in honour of the List of Roman deities, god Saturn (mythology), Saturn, held on 17 December in the Julian calendar and later expanded with festivities until 19 December. By t ...
'' and '' Chromogisaurus''. Using a modified version of this dataset, an article depicting a novel phylogenetic hypothesis for the position of
silesaurids Silesauridae is an extinct family of Triassic dinosauriforms. It is most commonly considered to be a clade of non-dinosaur dinosauriforms, and the sister group of dinosaurs. Some studies have instead suggested that most or all silesaurids compr ...
, two follow studies, as well as a study on early dinosaurs from South America based on another dataset also corroborated this position. The following is a cladogram showing ''Nhandumirim'''s placement using Cabreira ''et al.'' (2016)'s analysis:


References

{{Taxonbar, from=Q61736488 Saturnaliidae Dinosaur genera Carnian dinosaurs Santa Maria Formation Fossil taxa described in 2019 Dinosaurs of Brazil