Although it looked like a crocodile (and probably lived like the more terrestrial crocodylomorphs), it was not closely related to these creatures, instead being an example of parallel evolution.

[1] The genus was named by German paleontologist, Dr. Eberhard Fraas, in 1866, possibly after the Neckar river of southwestern Germany, near which it was found.

Some distinguishing anatomical features of Nicrosaurus are the external nares at the skull roof level, the dorsoventrally compressed and rounded posterior squamosal processes, the broad and heavy rostrum and a strong prenarial crest.

Occurring in marginal-lacustrine or outrightly terrestrial settings, it bears longer limb bones, a straighter femur and a deeper pelvis than other phytosaurs.

[4] In terms of jaw morphology, a full prenarial crest is a distinctive anatomical feature for Nicrosaurus kapffi.

[5] Nicrosaurus in general have massive snouts similar to extant crocodilians, suggesting they preyed on tetrapods instead of fish.

[6] All derived phytosaurs have an ilium that is characterized by a blade that elongates posteriorly and an anterior process that is short in length.

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.

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.

[1] 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.

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.

[6] 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.

[15] 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.