''Zambiasaurus'' is an extinct

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 ...

dicynodont Dicynodontia is an extinct clade of anomodonts, an extinct type of non-mammalian therapsid. Dicynodonts were herbivorous animals with a pair of tusks, hence their name, which means 'two dog tooth'. Members of the group possessed a horny, typicall ...

s that was discovered in the

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 and ...

(

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 Ep ...

) Ntawere Formation of

Zambia Zambia (), officially the Republic of Zambia, is a landlocked country at the crossroads of Central Africa, Central, Southern Africa, Southern and East Africa, although it is typically referred to as being in Southern Africa at its most cent ...

, southern Africa. It was a large

, reconstructed using several fossil fragments, in majority belonging to probably a juvenile ''Zambiasaurus submersus''. ''Zambiasaurus submersus'' is the

type species In 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 species that contains the biological type specimen ...

of the genus ''Zambiasaurus''. It is a

stahleckeriid Stahleckeriidae is a family of dicynodont therapsids whose fossils are known from the Triassic of North America, South America, Asia and Africa. Classification Phylogeny Below is a cladogram A cladogram (from Greek ''clados'' "branch" and ...

, the first

known outside

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 southe ...

, and it is also the oldest known

Description

Skull

The skull of ''Zambiasaurus submersus'' was reconstructed by using eighteen different juvenile

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

fragments and fragments of an adult Zambiasaurus. The immature skull had the dimensions of long and wide while the adults had a skull long and wide. There are no teeth in both upper and lower jaws making it a herbivorous species. Skull tapers

anteriorly Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

, widest across

occiput The occipital bone () is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobes of the cereb ...

. Wide inter-orbital region and narrow inter-temporal region. A blunt

snout A snout is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw. In many animals, the structure is called a muzzle, rostrum, or proboscis. The wet furless surface around the nostrils of the nose of many mammals is c ...

and a short median suture between nasals. Pineal foramen surrounded by parietals. Preparietal bone absent. Parietals slightly concave

antero-posteriorly Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

and from bulk of intertemporal bar.

Interparietal bone An interparietal bone (os interparietale or Inca bone or ''os inca var.'') is a dermal bone situated between the parietal and supraoccipital. It is homologous to the postparietal bones of other animals. In humans, it corresponds to the upper p ...

doesn't extend far forward. No sharp median intertemporal ridge. Sharp transition between dorsal and

occipital The occipital bone () is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobes of the cereb ...

surface. Occipital wings of squamosal extend laterally and somewhat posteriorly. Palatal surface of

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 mammal has b ...

bears pair of anterior ridges.

Post-cranial elements

Fragmented

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 showed the

prezygapophyses The articular processes or zygapophyses (Greek language, Greek ζυγον = "yoke" (because it links two vertebrae) + απο = "away" + φυσις = "-physis, process") of a vertebra are projections of the vertebra that serve the purpose of fitting ...

is concave and the

postzygapophyses The articular processes or zygapophyses (Greek ζυγον = "yoke" (because it links two vertebrae) + απο = "away" + φυσις = "process") of a vertebra are projections of the vertebra that serve the purpose of fitting with an adjacent vertebr ...

is convex. Fragments of ribs did not provide any useful information. Reconstructed from a lower and upper fragment, the

scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eithe ...

showed a long and narrow blade, low

scapular spine The spine of the scapula or scapular spine is a prominent plate of bone, which crosses obliquely the medial four-fifths of the scapula at its upper part, and separates the supra- from the infraspinatous fossa. Structure It begins at the vertical ...

running along the antero-lateral edge. Acromion process is not very large. Origin of scapular ligament of triceps muscle on postero-dorsal edge above the

glenoid The glenoid fossa of the scapula or the glenoid cavity is a bone part of the shoulder. The word ''glenoid'' is pronounced or (both are common) and is from el, gléne, "socket", reflecting the shoulder joint's ball-and-socket form. It is a sha ...

. There is no notch on the lower edge of the

so the

foramen In anatomy and osteology, a foramen (;Entry "foramen"
in

laid entirely inside the precoracoid. Fragments of

clavicle The clavicle, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between the shoulder blade and the sternum (breastbone). There are two clavicles, one on the left and one on the rig ...

provided no useful information. Sternum is hexagonal and ventral side is slightly concave. Dorsal side has postero-lateral bosses that have cartilage-ornaments on the ends. Reconstructed from two complementary fragments, the

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

is strongly twisted expressing very poorly muscular insertion and articulation areas. The

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

is also incomplete and reconstructed from two

distal Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

fragments. It is slender and configured to be longer than the

ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...

. A complete

shows a slender bone and convex distal ends.

Classification

''Zambiasaurus'' is characterized as a stahleckeriid, because of many shared characteristics such as; * Blunt

* Wide but low

* Short temporal opening * Lack of a high intertemporal crest * absence of preparietal * Nasals meet for a short distance in the midline or separated by a junction * Narrow neural spine similar to anterior vertebrae of juvenile ''

Stahleckeria ''Stahleckeria'' is an extinct genus of Middle Triassic (Ladinian) dicynodonts.Coracoid, Sternum, and

Pelvis The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). The ...

generally similar * Absence of tusks signify a close relation to ''

Stahleckeria ''Stahleckeria'' is an extinct genus of Middle Triassic (Ladinian) dicynodonts.Dinodontosaurus'' or '' Chanaria'', the other two Stakleckeriid

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

History

''Zambiasaurus'' was named after the country of origin

and ''Zambiasaurus submersus'' means the likelihood that the species drowned. Fossil reptiles were first found in upper

Luangwa River The Luangwa River is one of the major tributaries of the Zambezi River, and one of the four biggest rivers of Zambia. The river generally floods in the rainy season (December to March) and then falls considerably in the dry season. It is one of ...

valley by Dixey in 1928 and 1935. The area was later re-examined in 1960 and 1960 by Dr. A. R. Drysdall and James Kitching. They examined an area north-west of Sitwe for four months and collected almost 500

specimen Specimen may refer to: Science and technology * Sample (material), a limited quantity of something which is intended to be similar to and represent a larger amount * Biological specimen or biospecimen, an organic specimen held by a biorepository ...

s. Later an expedition to Sitwe was done by a joint effort of the

British Museum The British Museum is a public museum dedicated to human history, art and culture located in the Bloomsbury area of London. Its permanent collection of eight million works is among the largest and most comprehensive in existence. It docum ...

(Natural History) and

University of London The University of London (UoL; abbreviated as Lond or more rarely Londin in post-nominals) is a federal public research university located in London, England, United Kingdom. The university was established by royal charter in 1836 as a degree ...

. They spent six weeks collecting 220 specimens. Even though there was a large collection of specimens the specimens themselves were imperfect or poorly documented.

Paleobiology

Thought to be herbivorous because of the lack of teeth and movement of lower jaws that appeared to be efficient in

mastication Chewing or mastication is the process by which food is crushed and ground by teeth. It is the first step of digestion, and it increases the surface area of foods to allow a more efficient break down by enzymes. During the mastication process, th ...

. ''Zambiasaurus'' had a barrel shaped body that was strongly built but very slow. The body was held off the ground but it either had a sprawling stance or a more upright stance.

References

External links

The main groups of non-mammalian synapsids at Mikko's Phylogeny Archive
{{Portal bar, Paleontology Kannemeyeriiformes Anisian life Middle Triassic synapsids of Africa Fossil taxa described in 1969 Anomodont genera