In 1938, Ferdinand Broili described an exquisitely-preserved specimen of lizard, preserved top-side-up, from Jurassic-aged rock deposits in the municipality of Wintershof, Eichstätt, Germany.
The specimen came into the possession of the Bavarian State Collection of Paleontology and Historical Geology (BSPG), where it was prepared by L. Haimerl.
It consists of a nearly-complete skeleton, albeit with a crushed skull, a tail missing the tail after the fifth vertebra (probably the result of amputation and replacement by cartilage, and several vertebrae preserved only as impressions (but their presence could still be verified by the associated ribs).
A counterslab to the specimen also exists.
Today, the rock deposits are known to belong to the Altmühltal Formation, and the specimen and its counterslab are stored under the accession numbers BSPG 1937 I 1a and 1b.

Although he was unable to examine it first-hand, Broili noted from Christian Erich Hermann von Meyer's description of the type specimen of Ardeosaurus brevipes that it bore similarities to this specimen, but also that they had important differences in snout and frontal bone shape, as well as vertebral counts.
However, he hesitated to create a new genus due to the preservational state of the skull.
Thus, he assigned it to the genus Ardeosaurus with reservations as a new species, A.?
schröderi, named after his colleague J. Schröder. (
The current specific name is schroederi: by Article 32.5.2.1 of the International Code of Zoological Nomenclature, umlauts in German names published before 1985 must be deleted and be replaced with an "e" inserted as the next letter.)

Robert Hoffstetter formally recognized the distinction between A.?
schroederi and A. brevipes in 1953, and established a new generic name, Broilisaurus.
However, Oskar Kuhn had already named a stegocephalian amphibian with the same name in 1938; thus, in 1958, he established another generic name for the species, Eichstättisaurus. (
Again, due to the ICZN, the current generic name is Eichstaettisaurus.)
In 1963, Marguerite Cocude-Michel opined that E. schroederi really represented the same species as Homoeosaurus digitatellus, which had previously been named as a non-type species of Homoeosaurus in 1914 by N.M. Grier.
Thus, she created the new combination Eichstaettisaurus digitatellus.

Contrary to Cocude-Michel, Hoffstetter identified digitatellus as a member of Ardeosaurus separate from Eichstaettisaurus in 1964.
Even though Cocude-Michel was aware of Hoffstetter's paper, in 1965 she reiterated her argument and made no attempt to address Hoffstetter.
Hoffstetter responded in 1966, calling Cocude-Michel's synonymy "unbearable".
He noted that it would entail the revision of the diagnostic characteristics of Eichstatettisaurus to a point where it would be practically indistinguishable from Ardeosaurus, which would contradict her family-level separation of the two.
Subsequent literature has retained Eichstaettisaurus schroederi and Ardeosaurus digitatellus as separate, although they received little attention until Tiago Simões and colleagues published a redescription of both in 2017.
In 1938, Ferdinand Broili described an exquisitely-preserved specimen of lizard, preserved top-side-up, from Jurassic-aged rock deposits in the municipality of Wintershof, Eichstätt, Germany. The specimen came into the possession of the Bavarian State Collection of Paleontology and Historical Geology (BSPG), where it was prepared by L. Haimerl. It consists of a nearly-complete skeleton, albeit with a crushed skull, a tail missing the tail after the fifth vertebra (probably the result of amputation and replacement by cartilage, and several vertebrae preserved only as impressions (but their presence could still be verified by the associated ribs). A counterslab to the specimen also exists. Today, the rock deposits are known to belong to the Altmühltal Formation, and the specimen and its counterslab are stored under the accession numbers BSPG 1937 I 1a and 1b.
Although he was unable to examine it first-hand, Broili noted from Christian Erich Hermann von Meyer's description of the type specimen of Ardeosaurus brevipes that it bore similarities to this specimen, but also that they had important differences in snout and frontal bone shape, as well as vertebral counts. However, he hesitated to create a new genus due to the preservational state of the skull. Thus, he assigned it to the genus Ardeosaurus with reservations as a new species, A.? schröderi, named after his colleague J. Schröder. (The current specific name is schroederi: by Article 32.5.2.1 of the International Code of Zoological Nomenclature, umlauts in German names published before 1985 must be deleted and be replaced with an "e" inserted as the next letter.)
Robert Hoffstetter formally recognized the distinction between A.? schroederi and A. brevipes in 1953, and established a new generic name, Broilisaurus. However, Oskar Kuhn had already named a stegocephalian amphibian with the same name in 1938; thus, in 1958, he established another generic name for the species, Eichstättisaurus. (Again, due to the ICZN, the current generic name is Eichstaettisaurus.) In 1963, Marguerite Cocude-Michel opined that E. schroederi really represented the same species as Homoeosaurus digitatellus, which had previously been named as a non-type species of Homoeosaurus in 1914 by N.M. Grier. Thus, she created the new combination Eichstaettisaurus digitatellus.
Contrary to Cocude-Michel, Hoffstetter identified digitatellus as a member of Ardeosaurus separate from Eichstaettisaurus in 1964. Even though Cocude-Michel was aware of Hoffstetter's paper, in 1965 she reiterated her argument and made no attempt to address Hoffstetter. Hoffstetter responded in 1966, calling Cocude-Michel's synonymy "unbearable". He noted that it would entail the revision of the diagnostic characteristics of Eichstatettisaurus to a point where it would be practically indistinguishable from Ardeosaurus, which would contradict her family-level separation of the two. Subsequent literature has retained Eichstaettisaurus schroederi and Ardeosaurus digitatellus as separate, although they received little attention until Tiago Simões and colleagues published a redescription of both in 2017.
Eichstaettisaurus