Paläontologische Zeitschrift

, 83:499 | Cite as

Jaw biomechanics in the South American aetosaur Neoaetosauroides engaeus

Research Paper

Abstract

The function of the jaw apparatus and the possible dietary habits of the aetosaur Neoaetosauroides engaeus from the Triassic of South America were analyzed in comparison with Northern Hemisphere aetosaurs Desmatosuchus haplocerus and Stagonolepis robertsoni and the living short-snouted crocodile Alligator mississippiensis. The adductor and depressor jaw musculature of these was reconstructed on the basis of dental and skeletal comparisons with living closest relatives’ extant phylogenetic bracket (EPB), followed by the analysis of the moment arms of these muscles to infer feeding habits. The aetosaurian skull design indicates that the total leverage of the inferred jaw musculature provides force rather than speed. However, within aetosaurs, the high ratios of muscle moment arms to bite moments indicate stronger bites in the northern Hemisphere forms, and faster ones in Neoaetosauroides. These differences indicate more developed crushing, chopping, and slicing capacities, especially at the back of the tooth series for D. haplocerus and S. robertsoni; whereas it opens a window to consider different abilities in which speed is involved for N. engaeus. There are differences among aetosaurs in dental characteristics, position of the supratemporal fenestra, location of the jaw joint relative to the tooth row, and shape of the lower jaw. Neoaetosauroides does not show evidence of dental serrations and wear facets, probably consistent with a relatively soft and non-abrasive diet, for example soft leaves and/or larvae and insects without hard structures. It might be possible that Neoaetosauroides represents a tendency towards insectivorous feeding habits, exploiting a food source that was widespread in continental environments throughout the Triassic.

Schlüsselwörter

Archosauria Aetosaurus Neoaetosauroides Schädel funktionelle Anatomie Kiefermechanik 

Kurzfassung

Die Funktion der Kiefer und die möglichen Ernährungsgewohnheiten des Aetosauriers Neoaetosauroides engaeus aus der Trias von Südamerika wurden mit den Aetosauriern Desmatosuchus haplocerus und Stagonolepis robertsoni aus der nördlichen Halbkugel und dem lebenden kurzschnäuzigen Alligator mississippiensis verglichen. Die Adduktoren und Depressoren der Kiefermuskulatur wurden auf der Grundlage eines Vergleiches der Kiefer und Zähne mit den nächsten lebenden Verwandten rekonstruiert, und die Hebelarme dieser Muskeln wurde analysiert, um Rückschlüsse auf die Ernährungsweise zu gewinnen. Die Struktur des Schädels der Aetosaurier deutet darauf hin, dass die Hebelarme der rekonstruierten Kiefermuskeln eher auf Kraft denn auf ein schnelles Schließen der Schnauze angelegt sind. Allerdings deuten innerhalb der Aetosaurier das hohe Verhältnis der Hebelarme der Kiefermuskeln zu ihren Drehmomenten auf einen kräftigeren Biß bei den Formen aus der nördlichen Halbkugel hin, gegenüber einem schnelleren Biß bei Neoaetosauroides. Diese Unterschiede deuten darauf hin, dass die Kiefer von D. haplocerus und S. robertsoni besser zum zermahlen, schneiden und abbeißen geeignet waren, insbesondere im hinteren Bereich der Zahnreihe, während sie für N. engaeus andere Möglichkeiten eröffnen, bei denen die Schließgeschwindigkeit der Kiefer eine Rolle spielt. Unterschiede zwischen verschiedenen Taxa der Aetosaurier finden sich in der Struktur der Zähne, der Position des Supratemporalfensters, der Lage des Kiefergelenkes in Relation zur Zahnreihe und der Form des Unterkiefers. Neoaetosauroides zeigt keine Anzeichen von Serrationen oder Abnutzungsspuren an den Zähnen, was wahrscheinlich auf eine relativ weiche und nicht-abschleifende Nahrung hindeutet, wie zum Beispiel weiche Blätter und/oder Larven und Insekten ohne harte Panzer. Somit erscheint es möglich, dass Neoaetosauroides eine Tendenz zur insektenfressenden Ernährungsgewohnheiten aufweist, und somit eine Nahrungsquelle ausnutzte, die in kontinentalen Ökosystemen während der Trias überall weit verbreitet war.

Keywords

Archosauria Aetosauria Neoaetosauroides Skull Functional morphology Jaw biomechanics 

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Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Julia Brenda Desojo
    • 1
    • 2
  • Sergio Fabián Vizcaíno
    • 2
    • 3
  1. 1.Sección Paleontología de VertebradosMuseo Argentino de Ciencias Naturales “Bernardino Rivadavia”Buenos AiresArgentina
  2. 2.Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET)Buenos AiresArgentina
  3. 3.Departamento Científico Paleontología de VertebradosMuseo de La PlataLa PlataArgentina

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