Theropod Dinosaurs

The idea of sapient theropod dinosaurs, often nicknamed “dinosauroids”, has captured the imagination since the idea was first utilized by Aritsune Toyota’s 1977 novel A Shadow of the Past (Kaneko, 1997) and later popularized by Sagan (1977). In recent years, the focus of this concept has shifted away from the anachronistically anthropomorphic lizard-men of speculations past, and toward more feasible hypotheses consistent with the avian nature of Mesozoic theropods, particularly maniraptorian coelurosaurs. Consequently, the prospect of finding fossil evidence of dinosauroids should be based on current knowledge of theropod paleobiology, with respect to observational evidence of social and technological intelligence of modern birds. The ultimate

goal of this approach is the application of a morphology-based classification of avian tools to potential artifacts made by dinosaurs.
The most commonly proposed ancestor for a dinosauroid, following Russel & Séguin (1982), is a troodontid, similar to the late Cretaceous species Troodon (=Stenonychosaurus) inequalis (Dixon, 1988; Norman, 1991). Troodontids were an successful group of small predatory coelurosaurs that first appeared in Asia during the late Jurassic before spreading worldwide, and may have been sister taxa to the most basal family of true birds, the archaeopterygids (Hu et al., 2009; Zanno et al., 2011). The early evolutionary history of the family demonstrates a trend toward increased cursoriality, paralleling how modern ground hornbills originated from tree-dwelling ancestors that became more terrestrial (Brunet, 1971; Kemp, 2001). The cranial anatomy of advanced troodontids – particularly that of the optic schleral rings, middle ear cavities, and basisphenoid bulla – indicates that they were owl-like nocturnal predators with large eyes and asymmetrical ears (Currie, 1985; Makovicky et al., 2003; Castanhinha & Mateus, 2006; Schmitz & Motani, 2011). In contrast to most other bird-like coelurosaurus, the wing-like arms became more vestigial over time, leading to the toe claws being the primary tools for killing small burrowing mammals and ornithopod dinosaurs, a habit confirmed by claw-induced digging traces in preserved mammalian den complexes (Simpson et al., 2010).
It is unlikely that any known Mesozoic non-avian dinosaurs were as intelligent as the smartest birds and non-human mammals; even troodontids, which had unusually high brain-to-body ratios for coelurosaurs, would have had the smarts of an ostrich, one of the dumbest of all modern birds. Even with limited intellectual capabilities, however, theropods may have been more sociologically sophisticated than often assumed. For example, bonebeds of allosaurs, tyrannosaurs, and dromaeosaurs representing all age groups, as well as trackways, have been suggested to represent pack-living behavior, complete with reused nests and lairs (Maxwell & Ostrom, 1995; Bakker, 1997; Erickson et al., 2006; Coria & Currie, 2006; Li et al., 2008; Hone & Rauhut, 2010). Even if the larger assemblages were in fact aggregates of smaller family units or crèches driven by the lure of prey (Roach & Brinkman, 2007), it is possible that such aggregations may have utilized coordinated hunting strategies to bring down larger dinosaurs. Currie (1998) hypothesized a general model for gregarious hunting, based on ontogenic morphology in the tyrannosaur Albertosaurus sarcophagus, in which fast gracile juveniles corralled prey items toward the jaws of the adults. Furthermore, bite marks on many theropod skulls, signifying intraspecific antagonistic encounters, have been interpreted as evidence of hierarchy establishment during territorial disputes within the pack, not unlike those seen in modern lions and wolves (Tanke & Currie, 1998; Chure, 2000).
If such predatory theropods utilized rudimentary tools during pack-hunting, such artifacts likely resembled the myriad of wood, cobble, and fecal instruments preferred by modern birds.

Under the definition of Jones & Kamil (1973), “tool” in this case refers to an intentional extension of the animal’s body using physical object. Therefore, the act of a theropod dinosaur simply dropping the prey item onto a sharp rock to kill it, much as modern eagles and vultures drop bones and tortoise shells onto hard surfaces to crack them upon, does not qualify as direct tool use. If, however, the dinosaur were to fashion a stick into a spear to impale its victim, then it would qualify as a tool use (Alcock, 1972). Various forms of simple spears, blades, ropes, and lures are used by a plethora of modern birds, including birds of prey, herons, owls, parrots, and passerines (van Lawick-Goodall & van Lawick-Goodall, 1966; Higuchi, 1986; Levey et al., 2004). The later group, particularly the families Corvidae (crows, magpies, jays, etc.) and Fringillidae (true finches), demonstrates the most advanced examples of tool-making culture, in which younglings are taught the crafts by their elders and are encouraged to seek out more efficient materials (Millikan & Bowman, 1967; Hunt, 1996; Tebbich et al., 2004). Many tool-using birds exhibit the ability to count up to six using true numerical ability, as well as limited conceptualizations of self-awareness, language, object permanence, and theory of mind that pave the way for the evolution of comprehension and empathy (Hoh, 1998; Smirnova et al., 2000; Watye et al., 2002; Tebbich & Bshary, 2004; Emery, 2006; Pepperberg, 2006; Clayton et al., 2007; Raby et al.,

2007)
The search for possible dinosaurian tools use could benefit from a morphological classification of known avian zootechnology. This would be analogous to the morphometric systematics used to describe the progression of tool cultures throughout human evolution from Olduwan, Archeulean, Mousterian, Aurignacian, and Microlithic stone industries to post-Neolithic metallurgy (Ambrose, 2001; Greenfield, 1999). In lithic analysis, classification schemes rely on the unifacial or bifacial geometry of tool specimens, especially in terms of microwear data at knapped or flaked scars in conchoidal fractures, as well as the petrology of preferred rock assemblages used in tool making (Keeley, 1977; Pelegrin, 1993; Bleed, 2001; Wiederhold & Pevny, 2013). Also taken to account are the geometry of ichnological traces from possible tool use on plant and animal remains (McPherron et al., 2010), as well as the likelihood of lithic recycling in which instruments from previous culture are rediscovered and refashioned by tool scavengers, as reported in ethnographic accounts of some American and Australian aboriginal tribes (Amic, 2007). To date, none of the morphometric methods common in anthropological lithic analysis have been applied to a large-scale study of the evolution of tool-making in birds (Naish, 2014). If such methods were employed to generate a rough classification of modern avian tool types, paleontologists could potentially pinpoint fossil examples of tool use by prehistoric birds and perhaps non-avian dinosaurs. One day, we might find that mobs of Cretaceous troodontids used sharp-pointed twigs to probe prey out from deep burrows, where their claws couldn’t reach...