''Nhandumirim'' (meaning "small
rhea" in the
Tupi language
Old Tupi, Ancient Tupi or Classical Tupi (also spelled as Tupí) is an extinct Tupian language which was spoken by the aboriginal Tupi people of Brazil, mostly those who inhabited coastal regions in South and Southeast Brazil. It belongs to the ...
) 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 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 lon ...
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 ...
from the
Carnian
The Carnian (less commonly, Karnian) is the lowermost stage of the Upper Triassic Series (or earliest age of the Late Triassic Epoch). It lasted from 237 to 227 million years ago (Ma). The Carnian is preceded by the Ladinian and is followed by t ...
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 ...
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 ...
. It is currently considered a
saturnaliid sauropodomorph. The
type and only species, ''Nhandumirim waldsangae,'' is known from a single immature specimen including
vertebra
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
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 oth ...
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 st ...
.
''Nhandumirim'' is differentiated from other Santa Maria dinosaurs such as ''
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 ''Staurikosaurus' ...
'' and ''
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 ...
'' 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 (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...
led the describers of the genus and species to consider ''Nhandumirim'' ''waldsangae'' possibly the earliest
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 ...
, 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 Ornithis ...
.
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 lon ...
, closely-associated with ''
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 ...
'' and ''
Chromogisaurus
''Chromogisaurus'' is an extinct genus of saturnaliid sauropodomorph which existed in Argentina during the Late Triassic (Carnian) period. It is from the Cancha de Bochas, Valle Pintado member of the Ischigualasto Formation. It was a herbivore ...
''.
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 attached. In other words, a type is an example that serves to anchor or centralizes t ...
of ''
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 ...
'', ''
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 Late Triassic period (235–228 million years ago). It conta ...
'', ''
Gomphodontosuchus
''Gomphodontosuchus'' is an extinct genus of cynodonts. It was created to describe the species ''Gomphodontosuchus brasiliensis''.
Species
''Gomphodontosuchus brasiliensis'' was first collected in 1928 by Friedrich von Huene in Santa Maria Forma ...
'', 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 oth ...
, 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 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 vertebrae and they are intermediate in size between the cervical ...
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 stores are all owned by individual franchisees.
The chain has three different ...
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 (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, 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 ...
, 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 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 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
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
increase in length and gradually reduce the size of their
transverse processes
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...
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 with ventral keels in proximal caudals are ''
Dracoraptor'' (which had paired, not midline, keels) and ''
Efraasia
''Efraasia'' (pronounced "E-FRAHS-ee-A") is a genus of 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 Germany. It was named in 1 ...
'' (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.
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 (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...
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. 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 (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...
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'' is a large genus of over 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. It is the largest genus of plants in terms of described species. The genus is native to tempe ...
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 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. Its upper extremity is ...
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 kn ...
'' and
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 ...
s rather than the more curved bone of other dinosaurs. Isolated
phalanges
The phalanges (singular: ''phalanx'' ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones.
...
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 sauropods and horned dinosaurs. A claw is a highly modified ungual ...
s are triangular in cross section and curved, though not to the extent seen in more advanced theropods.
Classification
![Nhandumirim skeletal](https://upload.wikimedia.org/wikipedia/commons/9/9f/Nhandumirim_skeletal.png)
The describers of ''Nhandumirim'' tested its relations using two
phylogenetic analyses
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
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 moun ...
''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 t ...
to
neotheropods. This is supported by a wide
ischiadic peduncle and several traits of the
tibia
The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...
. 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 recovere ...
'', and ''
Eodromaeus
''Eodromaeus'' (meaning "dawn runner") is an extinct genus of probable 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) Ischigualasto Formation ...
'', 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 Ornithis ...
ns according to their results.
Adding ''Nhandumirim'' to the second analysis, created by
Nesbitt &
Ezcurra (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 tr ...
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 Ornithis ...
, along with several traditional basal theropods,
herrerasaurids, and ''
Eoraptor
''Eoraptor'' () is a genus of small, lightly built, basal sauropodomorph. One of the earliest-known dinosaurs, it lived approximately 231 to 228 million years ago, during the Late Triassic in Western Gondwana, in the region that is now northwest ...
'' (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 "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 ''Staurikosaurus' ...
'' or ''
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 ...
''.
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 c ...
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 lon ...
, close-associated with ''
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 ...
'' and ''
Chromogisaurus
''Chromogisaurus'' is an extinct genus of saturnaliid sauropodomorph which existed in Argentina during the Late Triassic (Carnian) period. It is from the Cancha de Bochas, Valle Pintado member of the Ischigualasto Formation. It was a herbivore ...
''.
Using a modified version of this dataset, an article depicting a novel phylogenetic hypothesis for the position of
silesaurids and two following studies also recovered ''Nhandumirim'' close-related to ''Saturnalia'' and ''Chromogisaurus''.
Another following study on early dinosaurs from South America based on another dataset once more considered ''Nhandumirim'' close-related to ''Saturnalia'' and ''Chromogisaurus''.
The following is a cladogram showing ''Nhandumirim''
's placement using Cabreira ''et al.'' (2016)'s analysis:
References
{{Taxonbar, from=Q61736488
Sauropodomorphs
Carnian genera
Late Triassic dinosaurs of South America
Triassic Brazil
Fossils of Brazil
Santa Maria Formation
Fossil taxa described in 2019
Paraná Basin