Samlinger Lokaliteter TidstavleFaunalister Blin


Alligatoroidea? overfamilie

 Faktiske data om fund 
Katalognummer:
676
Accessionsnummer:
DK 734
Samling:
Danekræsamlingen
Samler:
Statens Naturhistorisk Museum
Finder:
Mogens R. Madsen
Bestemt af:
Daniela Schwarz-Wings
Lokalitet:
Gemmas Alle, Amager
Stratigrafi:
Københavns Kalk
Periode:
Sen Danien
Type:
Sediment:
Echinoderm konglomerat

Billede

Foto ©: Sten Lennart Jakobsen


 Beskrivelse:   af  Daniela Schwarz-Wings 
Crocodylian tooth found by Mogens Madsen, Fredericia in samples of the Echinderm Conglomerate, collected during construction work by Gemmas Alle, Amager, in 1994.

The preserved tooth crown has a basoapical height of 20.4 mm and a basal maximum width of 14.5 mm. A large, basoapically oriented crack in the enamel divides the tooth crown on the lingual side and continues also labially, and two other cracks are visible around the tooth, disturbing also the mesial and distal carina. The cracks expose the underlying dentine.

The tooth crown is conical and blunt in habitus. The base of the tooth crown is circular, and the apex is narrow rounded. The tooth crown is only very slightly labiolingually compressed and very slightly curved along its long axis. The lingual side of the tooth crown is slightly less convex than the labial side. Visible, but weak carinae are present both on the medial and the distal side. The carinae start directly dorsal to the base of the tooth crown and fade ventral to its apex. The carinae are smooth and separated from the rest of the striated enamel only by their greater height and overall smoothness. The apex of the tooth crown is slightly worn, with the outermost layer of the enamel chipped off.

The enamel is both on the labial and on the lingual side strongly striated. This striation is produced by a pattern of deep grooves or flutes in the enamel. The numerous grooves extend straight from the base of the tooth crown until its apical part. Due to the tapering of the tooth crown, some of the grooves become wedged into surrounding ones and end in between, but none of them swerves laterally to reach the carinae. The striae end lingually at the dorsal fifth of the tooth crown, but labially extend slightly higher, into the dorsal sixth of the tooth crown.

The morphology and stratigraphic age (Echinoderm Conglomerate, Danian/Selandian Boundry) of the described tooth makes it most likely that the specimen belongs to a eusuchian crocodyliform with a rather generalistic dentition. In particular if minor differences in the striation pattern of the enamel are regarded only as variation and not as diagnostic, it becomes difficult to make a taxonomic assignment basing on only one isolated tooth. Two possibilities appear for a taxonomic assignment, although the preservation of features does not allow an unambiguous assignment: 1. The tooth might belong to Aigialosuchus, a longirostrine eusuchian in need of a taxonomic revision, 2. The tooth might belong to a member of Alligatoroidea. Members of Alligatoroidea are the most common crocodylians in the Late Cretaceous of Europe and present a high diversity of forms including more generalistic forms such as Allodaposuchus or Massaliasuchus and more specialized taxa such a Acynodon. Gavialoid crocodylians, in particular Thoracosaurus can be excluded because of their deviating tooth morphology.

Regardless of its assignments, the tooth is interesting in a stratigraphic context, as it belongs to one of the few Danian records of crocodylians in Europe in general and in Scandinavia in particular. Together with other reported direct and indirect evidence from the Faxe quarry, the tooth demonstrates the potential of this quarry to yield new crocodilian material, and proves that the earliest Paleocene of Northern Europe must have accomodated a more diverse crocodilian fauna than hitherto known. I can recommend that it is decleared Danekræ.

2014 Schwarz-Wings, D., Milàn, J. and Gravesen, P.
A new eusuchian (Crocodylia) tooth from the Early Paleocene Upper Crania limestone or “Echinoderm Conglomerate” of Copenhagen, Denmark: Implications for the Early Paleocene crocodylian diversity of Northern Europe.

Udtalelse på grundlag af valuarrapport af Arne Thorshøj Nielsen.
Fundet udgøres af en tandkrone, 20,4 mm høj, fra en krokodille. Tanden er flækket så det indre kan ses, desuden er spidsen slidt. Ydersiden er strieret og morfologien viser, at der sandsynligvis er tale om en repræsentant for underordenen Eusuchia. Det er dog svært at bestemme den nærmere eftersom der kun er tale om en isoleret tand idet tænders form er ret generel. Der foreligger to muligheder: Der kan være tale om Aigialosuchus eller en repræsentant for alligatorer. Sidstnævnte er de mest almindelige krokodiller i Øvre Kridt i Europa.

Uanset præcis identifikation er tanden ud fra et stratigrafisk synspunkt interessant, da fund af krokodilletænder af Danien alder er særdeles sjældne i Europa (DK 734 antages omlejret fra Danien kalk).

Det er grundet fundets store sjældenhed, kombineret med dets udstillingsmæssige værdi, der gør at det er erklæret danekræ.
Download hele den videnskabelige publikation, -
A new eusuchian (Crocodylia) tooth from the Early or Middle Paleocene, with a description of the Early-Middle Paleocene boundary succession at Gemmas Allé, Copenhagen, Denmark, fra Bulletin of the Geological Society of Denmark - Volume 62

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