Appearing in the Oligocene and peppering the fossil record into the Miocene (from approximately 25.8 - 10.3 million years ago), Leptocyon is a genus of small bodied canids endemic to North America. These canids, consisting of three species, L. gregorii, L. vafer, and L. vulpinus, represent the origins of the canine family tree as it diverged away from the feliniform carnivorans and the other caniforms. The caniforms include not only dogs, foxes, and wolves but also bears, seals and sea lions, and mustelids. For the approximately 15 million years of the fossil record that Leptocyon appears, it is the only canid that appears. Around the time that Leptocyon disappears from the fossil record an explosive diversification of foxes, wolves, coyotes, and wild dog begin to appear in the fossil record.
In the vein of an animal of importance to the native peoples of this continent, this precursor to so many different types of canines is the grandfather genus to many very impactful animals on the mythos and lore of those peoples. Wolves and coyotes are extremely important to many cultures of North America. Foxes, though, are just as important but not as prominently featured in Native American cultures as the other cultures. All of these animals star in other cultures globally (I wrote an honors thesis in undergrad on foxes in Japanese Shinto, for example) as well. Our discussion this week will elaborate on the origins of all of these animals from their humble beginnings in North America. The story of Leptocyon is the story of some of our favorite pets as much as it is the story of animals important to the native peoples of North America.
17 November 2017
15 November 2017
The egg of Argentavis is estimated to weigh approximately 1 kg and it has been hypothesized that they were laid once every two years. At 1 kg the egg is only a little smaller than that of the Common Ostrich, but Argentavis' egg laying cycles were similar to gulls and albatrosses rather than animals that reproduce annually. It has been hypothesized that the incubation cycle of these eggs was such that the birds were forced to incubate over winter. Chicks were thought to have lived with the parents for approximately 16 months before permanently leaving the nest. By contrast, the Wandering Albatross is the longest fledging extant bird, with the young bird remaining in the nest for 278 days. As with many extant gulls and other seabirds, Argentavis is thought to have then had a sexually dormant period, not achieving maturity until approximately 12 years old; Royal and Wandering Albatrosses reach maturity between 6 and 10 years. The fact that Argentavis was so large means that most predation and death probably occurred either in the nest or by from accidents and old age. How old Argentavis lived to be naturally is up for debate, but we know that a lot of extant birds, large and small, live extremely long lives today. The Kakapo of New Zealand is thought to live well over 100 years; with so few in the wild and their histories not being cataloged until recently, however, the oldest known member was approximately 80 at his death. Other parrots have been known to live into their 80's in captivity and individual Royal Albatrosses have been documented at 58 years old in the wild. The largest flying birds, Great Bustards, live to approximately 10 years, whereas the oldest eagles have been recorded at between 30 and 40 years old (depending on the species). All of these numbers make pinpointing the ages of large birds, especially those that can fly, difficult. Argentavis could have lived a lifespan like that of a large eagle, meaning that it could have lived up to 40 years. That means that an adult pair, laying one egg every two years, could have possibly reared 14 young during their lifespan. Not only a large bird, Argentavis may have had a rather sizeable population at one time or another because of their long lives, large size, and dedication to a single offspring.
14 November 2017
One of the questions that appears time and again with giant flying animals is "How do they get off the ground and how do they stay off the ground?" Because that is a popular theme with large flying animals, the first hit in a paper search for Argentavis is Chaterjee, et al. 2007: The aerodynamics of Argentavis, the world's largest flying bird from the Miocene of Argentina. The author's conclusions are centered around the hypothesized aspect ratio of the wing and estimated body weight. These parameters lead them to conclude that Argentavis was most likely similar to extant vultures and large condors in that it was probably not capable of sustained powered flight, instead choosing to use thermal soaring as its preferred method of staying airborne. Intermittent powered flapping would have been used as it is by these extant analogues as a secondary anti-stall measure but not as a power source for extended flight. This paper builds off of the new data and goes into more computer simulation than Vizcaino and and Farina1999, which initially tackled the problems of Argentavis flight without computer simulations, instead, it appears, relying on estimates of body size and inferred wing shape and comparing these with extant animals and known aerodynamic principals; the full text is not available anywhere online and what I have inferred comes from the abstract found here. The final article I will mention today addresses ecology (and reproduction). Palmqvist and Vizcaino 2003 details ranges, needed amounts of food, airspeeds, and clutch size to determine the ecological impacts and roles of Argentavis. Instead of spoiling this paper by writing in those facts, as I did above to a slight degree, I am going to simply encourage everyone to read and discover the paper's findings for themselves here. I find the paper to be interesting and find myself wondering if anyone would refute any of these findings; I have yet to find a paper that does so (I admit my search is short right now though).
13 November 2017
11 November 2017
10 November 2017
Probably the best Bison latifrons image I have seen this past week (before looking tonight as I write this sentence) is that of Davide Bonadonna that I shared on the Facebook version of this page. Rather than paste it in here without contacting Davide, I will link his gallery where he hosts his illustrations. A large majority of bison illustrations are not as exciting as Bonadonna's or include modern bison being attacked by wolves (if not a hunting scene with Native Americans. In the "non-action but still fun" category one of the best images I have seen this week is Christopher DiPiazza's B. latifrons at the watering hole. I think I like this image more because it shows an interesting level of curiosity not often associated with the big brutish bison and also because it has softer tones that contrast with a lot of the images we have looked at over the course of the week. Please feel free to share more illustrations that you like in the comments.