Panthera atrox

Davis, Matt, Nye, Benjamin D., Sinatra, Gale M., Swartout, William, Sjӧberg, Molly, Porter, Molly, Nelson, David, Kennedy, Alana A. U., Herrick, Imogen, Weeks, Danaan DeNeve & Lindsey, Emily, 2022, Designing scientifically-grounded paleoart for augmented reality at La Brea Tar Pits, Palaeontologia Electronica (a 9) 25 (1), pp. 1-37 : 17-19

Panthera atrox

( Figures 10 , 11 )

Appearance. For the muscle placement of our American lion ( Panthera atrox ) reconstruction, we followed (Cuff et al., 2017) who used a nearly complete skeleton found at the Tar Pits (LACMP23- 555) to digitally flesh out the species with realistic virtual muscles. General body shape followed a reconstruction by Mauricio Antón (2013a) and the appearance of extant African lions ( Panthera leo ).

While it is clear that American lions were closely related to African lions (Barnett et al., 2009) and followed their general body shape albeit at a much larger size, the pelage of American lions remains controversial (Yamaguchi et al., 2004). Recent descriptions (published after we developed our models) of several well-preserved frozen cubs of European cave lions ( Panthera spelaea ), the sister taxon to P. atrox (Tseng et al., 2014) , show that at least young of that species closely resembled extant African lions (Boeskorov et al., 2021). The European cave lions differed in several key respects though including lighter, greyer coats; thicker fur undercoats; and dark fur along the dorsal midline. Even though two of the European cave lions were thought to be 1–2 months old, they also lacked the dark, circular markings found on the coats of extant African lion cubs (Boeskorov et al.,

DAVIS ET AL.: LA BREA TAR PITS PALEOART

2021). The fur around the European cave lion cubs’ faces seem to be consistent with cave paintings of P. spelaea that frequently show a contrasting “drip line” descending from the eye to the cheek as well as a dark patch between the eye and ear (Boeskorov et al., 2021).

In contrast to the preserved soft tissues and cave art representations of the European cave lion, the American lion was known only from skeletal remains until Chimento and Agnolin (2017) reanalyzed the morphology of several South American fossils once attributed to a giant, extinct jaguar, “ Panthera onca mesembrina ”, and reassigned them to Panthera atrox . Based on skin associated with fossils of “P. o. mesembrina” and cave art, they reconstructed P. atrox as a large lion with a jaguar-like appearance including black spots over a rufous coat and yellowish striped forelimbs (Chimento and Agnolin, 2017). American lions and jaguars ( Panthera onca ) have often been mistaken for each other; in fact, all extant Panthera species possess highly similar skeletal morphology and are often difficult to distinguish by cranial characteristics alone (Christiansen and Harris, 2009). Metcalf et al. (2016) sampled 17 fossils of “P. o. mesembrina” from across South America for ancient DNA and found they all clustered into a genetically distinct clade sister to modern jaguars ( P. onca ), not modern African lions ( P. leo ). Twelve of these samples came from Cueva del Milodon in Ultima Esperanza, Chile: the same location of the skeletal and skin material examined in Chimento and Agnolin (2017). Crucially, a distal fragment of a right humerus (MLP 94-VIII-10-15) that Chimento and Agnolin (2017) assigned to P. atrox based on morphology had DNA that matched P. o. mesembrina instead (Metcalf et al., 2016). The isolated fragment of skin (MLP 94-VIII-10-71) pictured in Chimento and Agnolin (2017, figure 8) purported to be P. atrox looks more like the countershading on a mountain lion ( Puma concolor ) than the spots of a jaguar. Unfortunately, the rufous patch of skin associated with a “P. o. mesembrina” skull was not pictured. Additionally, the cave art evidence for a jaguar-like American lion seems overstated. Chimento and Agnolin (2017) claim that one spotted figure from El Ceibo, Santa Cruz province, Argentina (Cardich, 1987, figures 16 and 17) likely represents an American lion because it is reddish and larger than other animals portrayed at the same site. Could it not represent a giant, extinct subspecies of jaguar that there now seems to be ample morphological and genetic evidence for? Or a modern jaguar that the artist painted larger to reflect its importance (Chimento and Agnolin, 2017)? The various patches of skin Chimento and Agnolin (2017) attributed to P. atrox need to be genetically tested to ascertain whether they actually represent the coloration of American lions and an expansion of this species’ known range into South America.

Whether American lions had manes is also controversial. Summarizing various lines of evidence including prehistoric art clearly depicting both sexes, Yamaguchi et al. (2004) concluded that manes are a secondary sexual character that evolved with extant African lions and likely did not occur in extinct European cave lions ( P. spelaea ). Given that American lions probably evolved from a subpopulation of Beringean P. spelaea , it is likely that they lacked manes as well (Barnett et al., 2009). Guthrie (1990) pointed to cave art in Les Combarelles, France that he interpreted as a male lion with discrete dorsal and ventral manes that were not as contrastingly colored as modern African lion manes. However, this same painting has also been interpreted as a bison, not a lion (Yamaguchi et al., 2004).

To represent the uncertain appearance of American lions, we made two, somewhat chimeric models ( Figures 10 , 11 ). Overall, they follow extant African lions but have slightly redder coats and subtle spots patterns on their flanks. One model represents a lioness or generic maneless lion ( Figure 10 ). The second follows Guthrie’s (1990) reconstruction of a male lion with distinct dorsal and ventral manes ( Figure 11 ). So far, we have only used the lioness/generic maneless version in our AR experiences to skirt the question of whether male American lions possessed manes. If we were to make these models again, we would probably make the coats lighter and greyer to reflect new evidence from the frozen European cave lion cubs (Boeskorov et al., 2021) as well as move the jaguar-like spots lower on the body and legs or eliminate them all together. The dark drip lines and patches found on cave lions’ faces as well as the dorsal stripe should also be added but given the blocky coloration of our low poly style, incorporating fine features like this might be difficult.

Behavior. Given their close relationship and morphology, we used modern African lions as a locomotion reference for American lions. Whether the two species shared the same social structure remains controversial. Modern African lions are the only extant felids whose females live in groups. Cave art showing multiple lions together suggests that European cave lions lived in some kind of group (Yamaguchi et al., 2004). However, American lion remains are incredibly rare at the Tar Pits compared to the overabundant remains of presumably social dire wolves, coyotes, and saber-toothed cats ( Smilodon fatalis ) (Carbone et al., 2009). The model of tar pits as predator traps (Stock and Harris, 1992) for social species is consistent with observations in modern ecosystems, where social predators like spotted hyenas (Crocuta crocuta), and lions are the most common animals that come to investigate playbacks of prey distress calls in African parks (Carbone et al., 2009). Was the American lion solitary or merely rare in the region around the Pleistocene tar pits? Other solitary carnivores like mountain lions and bears ( Ursus arctos , U. americanus , and Arctodus simus ) are relatively rare in Tar Pits deposits (Carbone et al., 2009). We think showing the American lion alone or in pairs and triplets is reasonable given their phylogenetic affinities and avoids making any strong statements about whether they lived in large packs.

Saber-toothed Cat

Figures

FIGURE 10. Low poly reconstruction of a generic extinct American lion (Panthera atrox). To view this model in 3D, please see the online version of this article.

FIGURE 11. Low poly reconstruction of a male extinct American lion (Panthera atrox). To view this model in 3D, please see the online version of this article.