The foraging pits of the nine-banded armadillo, Dasypus novemcinctus (Mammalia: Xenarthra: Dasypodidae), and implications for interpreting conical trace fossils

Abstract

The nine-banded armadillo (Dasypus novemcinctus) is a well known burrower, but individuals spend the majority of their time above ground foraging for soil organisms by repeatedly digging pits through the soil surface. Little ichnological attention has been given to these foraging pits even though their great prevalence within the geographic range of extant armadillos implies that they might have a trace fossil record in paleosols extending back to at least the Paleocene. This research describes the foraging pits constructed by D. novemcinctus with implications for recognition and interpretation of similar conical trace fossils. Field observations yielded an association between one large-diameter (41 cm wide) dwelling burrow, three relatively short, straight shelter burrows (up to 19 cm wide and 38 cm long), and abundant variously sized foraging pits (up to 18 cm wide and 14.5 cm deep). Plaster casts of foraging pits showed that most were asymmetrical, vertically oriented, downward-tapering elliptical cones (width>depth), with smooth to coarsely dimpled walls and common elongate, parallel grooves, isolated curved grooves, and distinct paired grooves, resulting from scratching with the elongated middle two digits of the forelimb. Digital models of plaster casts are used to quantify several aspects, including a new property, conicality. Relative compactness and volume exploited indicate that surface pits are more efficient for soil foraging than subterranean burrows. Recognition of fossil armadillo foraging pits would enable paleoenvironmental and paleoclimatic interpretations analogous to the habitats and ranges of extant armadillos. Conical trace fossils in the Upper Jurassic Morrison Formation are potential examples of ancient vertebrate foraging pits, although they are not attributable to armadillos because of their age.

Wolf spider burrows from a modern saline sandflat in central Argentina: morphology, taphonomy and clues for recognition of fossil examples

“…8G ) are similar to the probing marks related to predation by small mammals, and similar structures are described in the literature including Sarzetti & Genise (2011) from northern Argentina, Suter, Stratton & Miller (2011) : Fig. 2 ), and Platt (2014) , the latter two from Mississippi, USA. Small mammals found in this area with similar behaviours are the armadillos and skunks.…”

“…Small mammals found in this area with similar behaviours are the armadillos and skunks. The more likely producer is a small armadillo as suggested by the size of the funnel and most importantly by the presence of sets of two large ridges in the cast surface (compare Platt, 2014 ), interpreted as scratch marks ( Fig. 8H ).…”

“…3B ). Finally, funnel shaped burrows can be compared with several ichnogenera including Monocraterion ( Torell, 1870 ); Conostichnus ( Lesquereux, 1876 ); Rosselia ( Dahmer, 1937 ); Conichnus ( Männil, 1966 ); and Cornulatichnus ( Carroll & Trewin, 1995 ) (see also Platt, 2014 ). A fundamental difference with these ichnogenera is the lack of large paired surface ridges, as seen in the predated Pavocosa sp.…”

Pachyosteosclerosis, rhamphotheca and enhanced sensory capabilities of the premaxillae of Hyperodapedon (Archosauromorpha, Rhynchosauria): implications for foraging at the sediment–water interface

“…The presence of a keratinized epithelium as a beak‐like structure is known in the chelonids (Wyneken 2001; Wu et al . 2004), extant birds (Louchart & Viriot 2011) and armadillos (Platt 2014), and also in extinct tetrapods such as the dicynodonts (King 1990; Jasinoski & Chinsamy‐Turan 2012; Benoit et al . 2018; Buffrénil et al .…”

Neoichnology of Armadillos: Keys for the Paleoecological and Behavioral Interpretation of Fossil Tetrapod Burrows

“…However, those studies commonly lack detailed information on the burrows that can be applied to the recognition of fossil examples. An exception is the work done by Platt (2014) on D. novemcinctus foraging pits. Identification of putative fossil armadillo burrows from sequences dating from the late Eocene to Holocene have relied essentially on the size (horizontal diameter) of the structures (e.g., Bown and Larriestra 1990; Quintana 1992; Vizcaíno et al 2001; Bellosi et al 2010; Cardonatto and Melchor 2018; Cardonatto 2019).…”