Calamosuchus

{{Short description|Genus of phytosaur reptiles}} {{distinguish|Calmasuchus}} {{Speciesbox | fossil_range =[[Late Triassic]], {{fossilrange|Carnian|Carnian|[[Carnian]] (Tuvalian substage)}} | image = Calamosuchus arenaceus (holotype, SMNS 80737).jpg | image_caption = Holotype specimen, labeled as ''[[Belodon]]'' (=''[[Nicrosaurus]]'') ''kapffi'' | display_parents = 4 | genus = Calamosuchus | parent_authority = [[Hans-Dieter Sues|Sues]] & Schoch, [[2025 in reptile paleontology|2025]] | species = arenaceus | authority = ([[Eberhard Fraas|Fraas]], 1896) | synonyms = * ''[[Zanclodon]] arenaceus''<br />{{small|Fraas, 1896}} * ''[[Belodon]] arenaceus''<br />{{small|(Fraas, 1896) [[Friedrich von Huene|Huene]], 1902}} * ''[[Phytosaurus]] arenaceus''<br />{{small|(Fraas, 1896) Schmidt, 1928}} * ''[[Mystriosuchus]] arenaceus''<br />{{small|(Fraas, 1896) [[Othmar Kühn|Kühn]], 1933}} | synonyms_ref=<ref name="A.H.2001" /> }}

'''''Calamosuchus''''' is an [[extinct]] genus of probable early [[phytosauria]]n reptiles known from the [[Late Triassic]] ([[Carnian]] age) [[Stuttgart Formation]] of Germany. The genus contains a [[Monotypic taxon|single species]], '''''Calamosuchus arenaceus''''', known from a partial [[mandible]]. The species was first described in 1896 by [[Eberhard Fraas]], who assigned it to the genus ''[[Zanclodon]]'' as ''Z. arenaceus''. Although researchers have noticed substantial differences between ''Z. arenaceus'' and the ''Z. laevis'' (the [[type species]]) since 1902, it did not receive a distinct genus name until 2025, when it was placed in the new genus ''Calamosuchus''.

== Discovery and naming == In 1869, the [[State Museum of Natural History Stuttgart]] (SMNS) obtained a partial [[mandible]] collected by Sixt Friedrich Jakob von Kapff, at which point it was identified as a specimen of ''[[Belodon]]'' (now ''[[Nicrosaurus]]'') ''kapffi''. The specimen was discovered in the Schilfsandstein ({{gloss|reed sandstone}}) deposits in [[:de:Feuerbacher Heide|Feuerbacher Heide]], representing outcrops of the [[Stuttgart Formation]] near [[Stuttgart-Feuerbach|Feuerbach, Stuttgart]], in Germany. The specimen is permanently [[Accession number (cultural property)|accessioned]] at this museum as specimen SMNS 80737.<ref name="Fraas1996" /><ref name="A.H.2001" /><ref name="S&S25" />

In 1896, German paleontologist [[Eberhard Fraas]] provided the first brief description of SMNS 80737, naming it as the [[holotype]] of a new species of the genus ''[[Zanclodon]]'', ''Z. arenaceus'', at that time thought—according to Fraas—to be a [[dinosaur]] without any doubt.<ref name="Fraas1996">{{Cite book |last1=Fraas |first=Eberhard |author1-link=Eberhard Fraas |title=Die schwäbischen Trias-Saurier, nach dem Material der Kgl. Naturalien-Sammlung in Stuttgart zusammengestellt. |publisher=E. Schweizerbart'sche Verlagsbuchhandlung |year=1896 |location=Stuttgart |pages=1–18 |language=de |url=https://hdl.handle.net/2027/uc1.c046894297}}</ref> The [[Specific name (zoology)|specific name]], ''arenaceus'', is a [[Latin]] word referring to sandy places,<ref name="M-W">{{Cite Merriam-Webster|arenaceous|access-date=2025-12-07}}</ref> alluding to the discovery of the specimen in the Schilfsandstein locality, literally translating to {{gloss|reed sandstone}}.<ref name="S&S25" />

In subsequent years, publications by researchers including [[Friedrich von Huene]] in 1902 and Frank Westphal in 1963 regarded the specimen as belonging to a member of the [[Phytosauria]]—a group of [[Convergent evolution|convergently]] crocodilian-like [[archosauriform]]s—instead of a dinosaur.<ref name="S&S25" /> Von Huene provided the first published figure of SMNS 80737, criticizing Fraas' identification of the specimen. Although he provided no anatomical evidence for his conclusions, he assigned the species to the phytosaur genus ''Belodon''. Later researchers accepted a phtyosaur placement for the species, not part of the genus ''Zanclodon'', proposing affinities with the genera ''[[Phytosaurus]]'' and ''[[Mystriosuchus]]'' as well. The first detailed description of SMNS 80737 was provided by Axel Hungerbühler in 2001, who confirmed the specimen is significantly distinct from ''Z. laevis'', the [[type species]] of ''Zanclodon'', and concluded it should not be treated as a member of this genus. Hungerbühler further noted phytosaur-like characters in the specimen, but also the lack of important phytosaur [[autapomorphies]] (unique derived traits). As such, "''Z.''" ''arenaceus'' was treated as Archosauria ''[[incertae sedis]]''. Hungerbühler refrained from naming a new genus for the material due to its fragmentary nature.<ref name="A.H.2001">{{Cite journal |last1=Hungerbühler |first1=Axel |date=August 2001 |title=The status and phylogenetic relationships of "''Zanclodon''" ''arenaceus'': the earliest known phytosaur? |journal=[[Paläontologische Zeitschrift]] |language=en |volume=75 |issue=1 |pages=97–112 |doi=10.1007/BF03022600 |issn=0031-0220}}</ref>

In 2025, [[Hans-Dieter Sues]] and Rainer R. Schoch published an extensive review of Triassic reptiles from Germany. Herein, they proposed a new genus name for "''Z.''" ''arenaceus'', forming the new combination ''Calamosuchus arenaceus''. The new [[Genus|generic name]], ''Calamosuchus'', combines {{lang|la|calamus}}, a Latin word meaning {{gloss|reed}}, with the [[Greek language|Greek]] word {{lang|grc|soûkhos}} ({{lang|grc|suchus}}), derived from the Greek name of [[Sobek]], the crocodile-headed [[Ancient Egyptian deities|deity of Ancient Egyptian myth]]. Like the specific name, this references the Schilfsandstein locality where the holotype was found, while '-suchus' is a suffix often used in reptile generic names.<ref name="S&S25">{{Cite journal |last1=Sues |first1=Hans-Dieter |last2=Schoch |first2=Rainer R. |date=2025-12-04 |title=Synopsis of the Triassic reptiles from Germany |journal=Fossil Record |language=en |volume=28 |issue=2 |pages=411–483 |doi=10.3897/fr.28.164405 |doi-access=free |issn=2193-0074}}</ref>

== Description and classification== The preserved mandible of ''Calamosuchus'' measures about {{convert|23|cm|in}} long, including at least the [[Mandible#Phylogeny|dentaries]] and [[splenial]]s. The [[Mandibular symphysis|symphysis]] (region where the two hemimandibles fuse at the midline) is {{cvt|11.5|cm|in}} long. The morphology of the fragmentary specimen indicates the mandible would have been greatly elongate in life. All of the visible teeth are incomplete; the right side has 15 [[alveoli]] (tooth positions) and nine preserved teeth. The teeth bear serrations, contrary to the condition in ''Zanclodon laevis'', which lacks them.<ref name="A.H.2001" />

In the 2001 redescription of SMNS 80737, a [[phylogenetic analysis]] was performed, recovering the specimen as the [[sister taxon]] to [[Phytosauria]]. However, Hungerbühler noted that, while this is the most parsimonious (best supported by the available data) position in the analysis, many characters separate it from phytosaurs and all other Triassic archosaurs studied at that time. The only characters he observed uniting "''Z.''" ''arenaceus'' with phytosaurs is the elongated mandible and mandibular symphysis, while it is different in all other features. Differences include the shape and proportional height of the mandible, the anterior (toward the tip of the snout) extent of the splenial, the tooth structure, and the absence of [[heterodonty]] (multiple tooth morphologies). As such, the species could not be assigned to the Phytosauria based on its definition at the time, and Hungerbühler refrained from redefining the clade to include "''Z.''" ''arenaceus''. Instead, he treated it more broadly as a member of the [[Archosauria]] with uncertain placement (''[[incertae sedis]]'').<ref name="A.H.2001" />

In their 2025 publication naming the new genus ''Calamosuchus'' for "''Z.''" ''arenaceus'', Sues and Schoch instead described it as Phytosauria ''incertae sedis'', suggesting it represents an early-diverging member of this clade.<ref name="S&S25" />

== Palaeoenvironment == ''Calamosuchus'' is known from the [[Stuttgart Formation]], which dates to the [[Carnian]] age of the [[Late Triassic]]. Other reptiles known from this formation include ''[[Henodus chelyops]]'' (a [[turtle]]-like [[placodontia]]n [[sauropterygia]]n), ''[[Thuringopelta werneburgi]]'' (a [[doswelliid]] [[proterochampsia]]n), and ''[[Dyoplax arenaceus]]'' (an [[erpetosuchid]] [[pseudosuchia]]n).<ref name="S&S25" />

== References == {{Reflist}}

[[Category:Phytosauria]] [[Category:Late Triassic reptiles of Europe]] [[Category:Carnian genera]] [[Category:Fossils of Germany]] [[Category:Fossil taxa described in 2025]] [[Category:Taxa named by Hans-Dieter Sues]]