''Nicrosaurus'' (/nɪkroʊˈsɔrəs/) is an extinct genus of

phytosaur Phytosaurs (Φυτόσαυροι in Greek, meaning 'plant lizard') are an extinct group of large, mostly semiaquatic Late Triassic archosauriform or basal archosaurian reptiles. Phytosaurs belong to the order Phytosauria and are sometimes ref ...

reptile existing during the

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. Although it looked like a

crocodile Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large, semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term "crocodile" is sometimes used more loosely to include ...

(and probably lived like the more terrestrial

crocodylomorph Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction. Extinct crocodylomorphs were considerably mor ...

s), it was not closely related to these creatures, instead being an example of

parallel evolution Parallel evolution is the similar development of a trait in distinct species that are not closely related, but share a similar original trait in response to similar evolutionary pressure.Zhang, J. and Kumar, S. 1997Detection of convergent and pa ...

. The main difference between ''Nicrosaurus'' (and all other phytosaurs) and modern crocodiles is the position of the

nostril A nostril (or naris , : nares ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbinates ...

s – ''Nicrosauruss nostrils, or external nares, were placed directly in front of the forehead (much like modern-day

cetaceans Cetacea (; , ) is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively c ...

(ie:

whales Whales are a widely distributed and diverse group of fully Aquatic animal, aquatic placental mammal, placental marine mammals. As an informal and Colloquialism, colloquial grouping, they correspond to large members of the infraorder Cetacea ...

dolphins A dolphin is an aquatic mammal in the cetacean clade Odontoceti (toothed whale). Dolphins belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontopori ...

porpoises Porpoises () are small dolphin-like cetaceans classified under the family Phocoenidae. Although similar in appearance to dolphins, they are more closely related to narwhals and belugas than to the true dolphins. There are eight extant speci ...

)), whereas in crocodiles, the nostrils are positioned on the end of the snout . A 2013 study has also found that ilium of ''Nicrosaurus'' is quite distinctive from all other phytosaurs. The genus was named by German paleontologist, Dr.

Eberhard Fraas Eberhard Fraas (26 June 1862 – 6 March 1915) was a German scientist, geologist and paleontologist. He worked as a curator at the Stuttgarter Naturaliensammlung and discovered the dinosaurs of the Tendaguru formation in then German East Africa (n ...

, in 1866, possibly after the

Neckar The Neckar () is a river in Germany, mainly flowing through the southwestern States of Germany, state of Baden-Württemberg, with a short section through Hesse. The Neckar is a major right tributary of the Rhine. Rising in the Schwarzwald-Baar ...

river of southwestern

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

, near which it was found.

Description and paleobiology

Some distinguishing anatomical features of ''Nicrosaurus'' are the external nares at the skull roof level, the dorsoventrally compressed and rounded posterior

squamosal The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestra ...

processes, the broad and heavy rostrum and a strong prenarial crest. ''Nicrosaurus'' may have been more terrestrial than other phytosaurs. Occurring in marginal-lacustrine or outrightly terrestrial settings, it bears longer limb bones, a straighter femur and a deeper pelvis than other phytosaurs. Combined with its unusually deep upper jaw and

heterodont In anatomy, a heterodont (from Greek, meaning 'different teeth') is an animal which possesses more than a single tooth morphology. Human dentition is heterodont and diphyodont as an example. In vertebrates, heterodont pertains to animals wher ...

teeth, it was most likely a secondarily terrestrial predator, probably not at all dissimilar from terrestrial crocodylomorphs like

sebecia Sebecia is an extinct clade of mesoeucrocodylian crocodyliforms that includes peirosaurids and sebecids. It was first constructed in 2007 to include '' Hamadasuchus'', Peirosauridae, and ''Sebecus''. It was initially considered to be the sister ...

ns.

Teeth

''Nicrosaurus'' dentition is highly

, the tooth shapes varying from wide, laterally compressed blade teeth to cylindrical, recurved caniniform teeth. In terms of jaw morphology, a full prenarial crest is a distinctive anatomical feature for ''Nicrosaurus kapffi''. In both the upper and lower jaw, the dentition has five morphologically separated arrays of teeth: tip-of-snout set, premaxilla set, maxilla set, tip-of-mandible set, and dentary set. Moving posteriorly in all of these sets, except the tip-of-the-snout and tip-of-mandible sets, tooth morphology starts out relatively simple and undifferentiated and gradually changes, resulting in a morphocline. The upper dentition is considered to be tripartite. The anteriormost teeth, or carinae, of the premaxilla set in ''Nicrosaurus kapffi'' are enlarged and strongly curved. These are usually the largest teeth of the upper jaw. Much of the other anterior teeth in this set, as well as in the maxilla, are difficult to distinguish from one another. The anteriormost teeth of the premaxilla are firmly anchored and labially vaulted. The number of tooth positions is highly variable for the premaxilla and maxilla set. However, no studies indicate that there is a direct correlation between tooth count and skull size. Teeth rows usually consist of 40-45 members. The tripartite dentition, enlarged

carinae ''Carinae'' was an area of ancient Rome. It was one of its most exclusive neighborhoods, where many of the senatorial class lived. Florus described the ''Carinae'' as the "''most celebrated part of the city''" (''celeberrima pars urbis''). Desc ...

,(incorrect link) and strong terminal members of the premaxilla suggest that ''Nicrosaurus kapffi'' (and many other phytosaurs) may be adapted to dismember medium to large-sized prey after killing such prey with a strong, quick blow. ''Nicrosaurus'' in general have massive snouts similar to extant crocodilians, suggesting they preyed on

tetrapods A tetrapod (; from Ancient Greek τετρα- ''(tetra-)'' 'four' and πούς ''(poús)'' 'foot') is any four- limbed vertebrate animal of the clade Tetrapoda (). Tetrapods include all extant and extinct amphibians and amniotes, with the lat ...

instead of fish.Kimmig, J., & Arp, G. (2010). Phytosaur remains from the Norian Arnstadt Formation (Leine Valley, Germany), with reference to European phytosaur habitats. Palaeodiversity, 3, 215-224.

Distinctive post-cranial features

All derived phytosaurs have an ilium that is characterized by a blade that elongates posteriorly and an anterior process that is short in length. However, compared to all phytosaurs, the ilium of ''Nicrosaurus kapffi'' is dorso-ventrally elongated, similar to that of ''Erythrosucus africanus.'' Because of the elongation, the

acetabulum The acetabulum (; : acetabula), also called the cotyloid cavity, is a wikt:concave, concave surface of the pelvis. The femur head, head of the femur meets with the pelvis at the acetabulum, forming the Hip#Articulation, hip joint. Structure The ...

is also longer relative to other phytosaurs. Compared to ''Leptosuchus'' the angle between the pubis and ischium is also greater. In ''Nicrosaurus'', the proximal end the humerus is flattened.Kimmig, J. 2013. Possible secondarily terrestrial lifestyle in the European phytosaur Nicrosaurus kapfii (Late Triassic, Norian): a preliminary study. Bulletin of the New Mexico Museum of Natural History and Science 61, 306-312.

Semi-aquatic or terrestrial nature

Because of their resemblance to modern crocodiles, it was initially thought that phytosaurs were also semi-aquatic animals. The slender jaws further suggested a diet containing fish. An earlier study explained that more massive ''Nicrosaurus'' could have also had a diet consisting of large land reptiles which came near waters or amphibians of streams and ponds.Gregory, J. T. (1972). Vertebrate faunas of the Dockum Group, Triassic, eastern New Mexico and west Texas. New Mexico Geological Society Guidebook, 23, 120-23. When it comes to phytosaurs, most inferences on ecology are in comparison with modern day crocodilians. However, genera within phytosaurs may also have had different ecological preferences. Such is the case for ''Nicrosaurus'' and ''

Mystriosuchus ''Mystriosuchus'' (meaning "spoon-crocodile")
Retrieved on May 25th, 2008. is an

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'', the biggest distinguishing factor between the two being the shape of their snouts. The latter had a slender skull with bipartite dentition, suggesting a diet of fish and small tetrapods, while the former had a massive skull with tripartite dentition, suggesting prey were larger animals. ''Nicrosaurus'' and ''Mystriosuchus'' have both been recovered in the first and second Stubensandstein in arkosic sandstones separated by floodplain mudstones and were both buried during flooding events in a freshwater river habitat. Both genera appeared at around the same time in central Europe. Additionally, because ''Nicrosaurus'' has also been found lacustrine sandstones, aerially exposed planes with breccia and reworked palaeosols, a terrestrial and swamp-inhabiting lifestyle seems probable. A more recent analysis on available post-cranial bones has provided results that further support the idea of ''Nicrosaurus'' being primarily terrestrial. The ilium and femur of ''Nicrosaurus'' are similar to those of

Archosaurs Archosauria () or archosaurs () is a clade of diapsid sauropsid tetrapods, with birds and crocodilians being the only extant taxon, extant representatives. Although broadly classified as reptiles, which traditionally exclude birds, the cladistics ...

in comparison to semi-aquatic Archosaurs, like today's crocodiles. The resemblance suggests ''Nicrosaurus'' could have had a more upright walking style that is often associated with terrestrial organisms.

Diet

A study on phytosaur microwear patterns shows that ''Nicrosaurus'' plots with hard invertebrate consumers.

Species Characters

The following are a list of characters for both species of ''Nicrosaurus'' following a phylogenetic analysis. ''Nicrosaurus kapffi'' (Meyer, 1860): SMNS 4378, 4379, 5726, 5727; NHMUK PV OR 43743. ''Nicrosaurus meyeri'' (Hungerbühler and Hunt, 2000): SMNS 12598 (holotype), 4059; NHMUK PV OR 42745.

''Nicrosaurus kapffi''

*Long snout *Ventrally convex alveolar rim of maxilla *Tripartite upper dentition * Posterior rim of nares behind anterior rim of antorbital fenestra *Infranasal recess present *Reduced antorbital fossa *Convex interorbitonasal fenestra *Strongly developed medial lamella of postorbito-squamosal bar, supratemporal fenestra reduced to slit *Medial parts of squamosal processes of parietals overhand supraoccipital shelf *Moderate depression of parieto-squamosal bar (bar 15-25% of absolute skull height) *Gently sloping dorsal edge of parieto-squamosal bar *Squamosal, dorsoventral expansion: strongly thickened, dorsal surface of squamosal raised terminally *Deep supraoccipital shelf *Posttemporal fenestra delimited by contact of parietal process of squamosal, ventrolateral border of posstemporal fenestra *Significantly reduced quadrate foramen *Interpremaxillary fossa: narrow slit *Anterior extent of palatine: tip extends forward beyond the posterior rim of choana *Lateral extent of palatines: extend onto palatal vault and meet along the midline *Suborbital fenestra: reduced to a singular oval fenestra, or subdivided into two or more small openings *Length of interpterygoid vacuity: tiny oval indentation at posterior rim of cojoined pterygoids

''Nicrosaurus meyeri''

*Very long snout *Bipartite upper dentition *Anterior extent of septomaxilla: posterior to or at level with anterior tip of nasal *Position of nares: posterior rim of nares behind anterior rim of antorbital fenestra *Infranasal recess is present *Reduced antorbital fossa *Convex interorbitonasal area *Moderately developed medial lamella of postorbito-squamosal bar *Medial parts of squamosal processes of parietals overhang supraoccipital shelf *Moderate depression of parieto-squamosal bar (15-25% absolute skull height) *Gently sloping dorsal edge of parieto-squamosal bar *Medial rim of squamosal along supratemporal fenestra (and posterior process): angular * Length of posterior process of squamosal: moderate *Lateral flange of the squamosal is absent and present *Subsidiary opisthotic process of squamosal is present *Depth and shape of supraoccipital shelf: deep, axis of shelf with steep slope anteriorly and terminal horizontal deflection of shelf *Posttemporal fenestra, lateral border: delimited by the contact of the parietal process of the squamosal (dorsal border) and the paroccipital process (ventral border); lamina of the squamosal extends onto the paroccipital process, forming the ventrolateral border of posttemporal fenestra *Exoccipital and supraoccipital shelf: broad, overhang foramen magnum and occipital condyle *Significantly reduced quadrate foramen *Interpremaxillary fossa: present, narrow slit *Anterior extent of palatine: tip extends forward beyond the posterior rim of choana *Lateral extent of palatines: extend onto palatal vault and meet along the midline *Suborbital fenestra: elongated, slit-like *Length of interpterygoid vacuity: tiny oval indentation at posterior rim of cojoined pterygoids

Discovery and environment

Species ''Nicrosaurus kapffi'' and the less commonly found ''Nicrosaurus meyeri'' occur in the Norian Stubensandstein of southwestern Germany, as well as from the Norian Arnstadt Formation. Since 1996, the collection for ''Nicrosaurus kapffi'' included five nearly complete skulls and four partial skulls. The

Arnstadt Formation The Trossingen Formation, formerly the Knollenmergel (also known as the Arnstadt Formation), is a geological formation in Germany and Switzerland. It dates back to the late Norian-Rhaetian. It belongs to the Keuper Group of the Germanic Triassi ...

, or "Steinmergelkeuper", is primarily a

lacustrine A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from t ...

sedimentary succession of the

Germanic Basin The Germanic Basin () is a large region of sedimentation in Western and Central Europe that, during the Permian and Triassic periods, extended from England in the west to the eastern border of Poland in the east. To the south it is bounded by the ...

. The 100m thick Formation is divided into sediments of a playa lake system, cyclic sediments of freshwater to saline lake system, and sediments of a playa lake system with crevasse splay. Fossil discoveries in Germany were found in dry floodplain environments or fluvial lacustrine indet., where the environment was known to be associated with either rivers or lakes or both. An isolated tooth found in a bed among fish scales in the middle part of Arnstadt Formation in 2002 was attributed to ''Nicrosaurus''. The rock in which the tooth and scales were found may suggest that a species of ''Nicrosaurus'' populated a swamp-like area that underwent periods of desiccation or fluctuations in salinity. Alternatively, the lone tooth may suggest that a scavenger fed on dead fish. If the lifestyle of ''Nicrosaurus'' is limited to land and freshwater swamps it makes sense that most of fossil specimens are found around the Germanic Basin.

Lithology

Specimen have been found in various bed lithology, including sandstone, marl, dolomite, breccia, and claystone.

Classification

Nicrosaurus - Cleveland Museum of Natural History

A 2002 phylogenetic analysis found that the genera ''

Machaeroprosopus ''Machaeroprosopus'' (from , 'large knife' and , 'bordering on') is an extinct genus of mystriosuchin leptosuchomorph phytosaur from the Late Triassic of the southwestern United States. ''M. validus'', once thought to be the type species of ''M ...

'', ''

Mystriosuchus ''Mystriosuchus'' (meaning "spoon-crocodile")
Retrieved on May 25th, 2008. is an

< ...

'', ''

Redondasaurus ''Redondasaurus'' is an extinct genus or subgenus of phytosaur from the Late Triassic (late Norian or Rhaetian) of the southwestern United States. It was named by Hunt & Lucas in 1993, and contains two species, ''R. gregorii'' and ''R. bermani''. ...

'' and ''Nicrosaurus'' are all under the clade Mystriosuchini. Though, the analysis only contained one non-mystriosuchin phytosaur taxon. If ''Mystriosuchus'' and ''Ebrachosuchus neukami'' were to be sister taxa, the tree length would be 119. ''Nicrosaurus'' is considered the most basal taxon of the clade.Hungerbühler A. 2002. The Late Triassic phytosaur ''Mystriosuchus westphali'', with a revision of the genus. ''Palaeontology'' 45 (2): 377-418

Species inconsistency

Beyond the ''Nicrosaurus kapffi'' and ''Nicrosaurus meyeri'', there are two other species mentioned in scientific literature: ''Nicrosaurus gregorii'' and ''Nicrosaurus buceros''. The remains of the latter two were found in North America, from the Chama basin of north-central New Mexico.

''Nicrosaurus gregorii''

When phytosaur remains were thought to be first found in North America scientists attempted to categorize them into major groups. However, at the time specimen were often referred to specific genera based on character similarities without giving much regard to the differences. Such was the case when

Herbert E. Gregory Herbert Ernest Gregory (October 15, 1869 – January 23, 1952) was a Yale University geologist well known for his early 20th-century explorations of the Colorado Plateau in Arizona and Utah. One of his most important works is ''Colorado Plateau R ...

referred ''Rutiodon gregorii'' to ''Nicrosaurus''. In the early 1960s, Gregory did not recognize the differences among phytosaurs like ''

'', '' Leptosuchus'' and ''

Rutiodon ''Rutiodon'' (meaning "wrinkle tooth") is an extinct genus of mystriosuchine phytosaurs from the Late Triassic of the eastern United States. The type species of ''Rutiodon'', ''Rutiodon carolinensis'', encompasses a large number of skulls and as ...

'' and attributed the variance to growth,

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

or individual variance. Most of the species of ''Machaeroprosopus'' were assigned to ''Rutiodon'' except for ''M. gregorii'' which was assigned as ''Phytosaurus gregorii'' because of the attributes it shared with European phytosaurs. ''Phytosaurus gregorii'' was later assigned as ''Nicrosaurus gregorii'' because of observed similarities in skull characteristics.Ballew, K. L. (1989). A phylogenetic analysis of Phytosauria from the Late Triassic of the western United States. Dawn of the Age of Dinosaurs in the American Southwest. New Mexico Museum of Natural History, Albuquerque, 309-339. The

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 ...

was defined first in 1917 by Herbert E. Gregory and many Norian-age vertebrae fossils were recovered from the deposit levels. Some of the skulls discovered in this region were said to be incorrectly assigned to ''Nicrosaurus'' instead of ''Rutiodon''.Murry, P.A. and Long, R.A., 1989. Geology and paleontology of the Chinle Formation, Petrified Forest National Park and vicinity, Arizona and a discussion of vertebrate fossils of the southwestern Upper Triassic; in Lucas, S.G. and Hunt, A.P., eds., Dawn of the age of dinosaurs in the American Southwest: Albuquerque, New Mexico Museum of Natural History, p. 29-64.

''Nicrosaurus buceros''

The first phytosaur taxon discovered in North America was believed to be from a skull of ''Belodon buceros'' in 1881 in the Chama basin, of north-central New Mexico. The species has also been attributed to other genera, including ''Pseudopalatus'', ''Phytosaurus'', ''Machaeroprosopus'', ''Arribasuchus'' and ''Nicrosaurus.'' Some attributed the skull type to ''Nicrosaurus'' because of a few cranial characteristics, pertaining to the squamosal and supra-temporal fenestra. In comparison to ''Nicrosaurus kapffi'', it carried a more narrow snout and therefore was referred to as ''Nicrosaurus buceros'' by some scientists.Zeigler, K. E., Lucas, S., Heckert, A., & Hunt, A. (2001, April). The phytosaur Nicrosaurus buceros in the upper triassic of the Chama basin, north-central New Mexico. Geological Society of America Abstracts with Programs, (Vol. 33, No. 5, p. 22).

References

{{Taxonbar, from=Q5224431 Phytosauria Prehistoric reptile genera Late Triassic reptiles of Europe Late Triassic reptiles of North America Fossil taxa described in 1866 Taxa named by Eberhard Fraas