Abstract
Despite their significance for paleobiological interpretations, bite marks have been rarely reported in non-mammalian therapsids (NMT). Here we describe, for the first time, the occurrence of a tooth embedded in the snout of a gorgonopsian. The tooth is surrounded by a bony callus, which demonstrates that the animal was still alive after the attack and healed. The identity of the attacker is unknown. Two hypotheses are discussed to account for this healed bite: failed predation (most likely by a biarmosuchian, therocephalian, or another gorgonopsian) and intraspecific social biting. Though predation cannot be ruled out, it has been hypothesized that gorgonopsians used their saber-like teeth for social signaling, which suggests that social biting may be the most likely scenario. The practice of social biting has long been hypothesized in NMT, but this is the first fossilized evidence of the behavior to be described.
Highlights
The presence of a callus around the embedded tooth clearly distinguishes SAM-PK-11490 from cases of post-mortem bites (e.g., Bell and Currie, 2010; Fordyce et al, 2012) as it unmistakably indicates that healing of the periosteum took place after the tooth broke-off
The vascularized surface and slightly elevated aspect of the callus observed in SAM-PK-11490 conforms well with healed bite marks documented elsewhere in other tetrapods (Scott and Jepsen, 1936; Lingham-Soliar, 2004; Zammit and Kear, 2011; DePalma et al, 2013; Chimento et al, 2019)
This is extremely significant as only postmortem damage (Budziszewska-Karwowska et al, 2010; Fordyce et al, 2012), bone infection caused by a bite (Shelton et al, 2019), or bone diseases unrelated to bites (Vega and Maisch, 2014; Kato et al, 2020) have been described in non-mammalian therapsids (NMT) to date
Summary
The paleopathological study of extinct species is the gateway to many, otherwise inaccessible, paleobiological traits such as intraspecific behavior (Farke et al, 2009; Peterson and Vittore, 2012; Peterson et al, 2013), diet and food acquisition (DePalma et al, 2013), etiology and healing capabilities (Wolff et al, 2009; Kato et al, 2020), soft tissue reconstruction (Rega et al, 2012), thermophysiology (Benoit et al, 2015), interspecific interactions (Aureliano et al, 2021), biting force (Erickson et al, 1996; Gignac et al, 2010), and even key transitional events in the evolutionary history of vertebrates such as the onset of arboreality in hominins and terrestriality in early tetrapods (Bishop et al, 2015; Kappelman et al, 2016). In particular, have been documented in countless fossil mammals (e.g., Scott and Jepsen, 1936; Tanke and Currie, 1998; Chimento et al, 2019), pelycosaurs (Reisz and Tsuji, 2006; Bakker et al, 2015), and outside synapsids in, e.g., dinosaurs, crocodilians, mosasaurs, ichthyosaurs (Buffetaut, 1983; Boucot, 1990; Rothschild and Martin, 1993; Tanke and Currie, 1998; Mackness and Sutton, 2000; Tanke and Rothschild, 2002; Avilla et al, 2004; Katsura, 2004; Lingham-Soliar, 2004; Zammit and Kear, 2011; Bastiaans et al, 2020), but remain rarely reported in NMT. For the first time, the preservation of a tooth found embedded in a callus within the bone of the snout of a gorgonopsian from South Africa, and discuss its paleobiological implications
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