Archive for June, 2022

Mauricio Anton’s New Reconstruction of the Scimitar-toothed Cat’s (Homotherium latidens) Face

June 29, 2022

Most people don’t know there were 2 species of fanged cats living in North America during the Pleistocene. Smilodon fatalis is the more famous species because fossil specimens of this extinct animal are relatively abundant, especially from the La Brea Tar Pits fossil site in California. But there was a lesser-known species that was more widespread, ranging from Africa across Eurasia to Florida. This species is often referred to as the scimitar-toothed cat. In Africa and Eurasia it is given the scientific name Homotherium latidens, and in North America it’s given the scientific name H. serum, but genetic evidence suggests they could be considered the same species. Despite a widespread geographic distribution, the genetic evidence also suggests the scimitar-toothed cat existed in low population numbers. It is uncommon in the fossil record, and in Europe there is a large gap in occurrence. Fossil evidence of H. latidens is known from a 300,000-year-old fossil site but is not recorded again in Europe until a specimen was found dating to 28,000 years ago in the North Sea which was above sea level at that time. Although it was never a common animal, the scimitar-toothed cat was a long-lived species, originally evolving during the late Pliocene and not becoming extinct until the late Pleistocene–a time span of over 2 million years. Evidence from the Friesenhahn Cave site in Texas indicates it may have specialized in hunting juvenile mammoths and mastodons in North America. Some think it must have hunted in packs, but it may have had a technique that made individuals capable of bringing down much larger prey. They had unusual sloping backs, much like modern spotted hyenas.

Mauricio Anton is a talented paleo artist who beautifully illustrated the excellent book The Big Cats and their fossil relatives. He works with paleontologists to produce anatomically accurate drawings of extinct species of cats and other animals. His original drawing of the scimitar-toothed cat depicted the fangs protruding when it mouth was closed. However, in a recent study involving 3 scientists, he determined the fangs on this species did not protrude when its mouth was shut.

Images of scimitar-toothed cat and a tiger skull and jaw.
Maricio Anton’s new reconstruction of a scimitar-toothed cat’s face. He now believes its fangs didn’t protrude when its mouth was closed. However, he does think the saber-toothed cat (Smilodon fatalis) did have protruding fangs when its mouth was closed.

For this study Anton and his colleagues looked at cat scans of extant big cat skulls and jaws and watched videos of them yawning and opening and closing their jaws. They also re-examined the skulls and jaws of Homotherium specimens. They concluded the fangs were not exposed when the scimitar-toothed cat closed its mouth. They still think the more famous species of saber-toothed cat (Smilodon fatalis) did have exposed fangs when its mouth was closed. The fangs on the latter species were much longer. Other species of pre-historic cats and cat-like species may or may not have had exposed fangs when their jaws were shut, depending upon the characteristics of each individual species.

Note on the reference: In the paper below they refer to the scimitar-toothed cat as the saber-tooth cat for its common name. I prefer to call it the scimitar-toothed cat to prevent confusion with its more famous relative.

Reference:

Anton, M.; G. Siliceo, J. Pastor, and M. Salesa

“Concealed Weapons: A Revised Reconstruction of the Facial Anatomy and Life Appearance of the Sabre-toothed Cat Homotherium latidens (Felidae, Machairodontinae)”

Quaternary Science Review 284 2022

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New Study Supports Human Overkill as cause of Megafauna Extinctions in the Middle East

June 22, 2022

The Middle East is a gateway between African and Eurasian faunas. Elephants, humans, and big cats among other animals originally evolved in Africa and spread through the Middle East to Eurasia and beyond. The Middle East, also known as the Levant, encompasses Israel, the Sinai Peninsula, Jordan, Lebanon, and Syria. Humans and their evolutionary ancestors beginning with Homo erectus have had a continuous presence in the region for at least 1.5 million years, and it is a good place to study the historical interaction between human species and Pleistocene megafauna. A recent survey of data from 58 archaeological sites in the Levant concluded the average size of the animals humans hunted declined over time throughout the past 1.5 millions years. The study also compared this data with temperature changes and changes in paleoenvironmental conditions and found little correlation between these factors and the decline in average animal body size. Therefore, they determined human hunters were entirely responsible for the disappearance and/or decline of megafauna populations from this region.

Map of the sites surveyed in the below referenced study.
Graph showing the decline in megafauna body size over the past 1.5 million years from archaeological sites located in the Middle East. From the below referenced study. The authors attribute this to human hunting, not changes in climate or paleoenvironmental conditions.

Africa did not experience many extinctions during the late Pleistocene as other parts of the world did when humans colonized new territory. However, there was a spike in extinctions of large mammals in Africa during the beginning of the Pleistocene. One example is an extinct species of giant baboon (Therepithecus oswaldi), an animal that occupied a similar niche as Homo erectus. There is direct evidence of Homo erectus killing 90 giant baboons at a site in Kenya, and I have no doubt they are responsible for the extinction of this species. Some scientists believe some species of megafauna were able to persist in Africa because the animals there co-evolved with man and had time to learn better survival strategies than megafauna in other parts of the world. Although this may be partly true, I think African megafauna survived to the present because large parts of the continent were frequently depopulated and uninhabited by man due to tropical diseases and intertribal warfare. Megafauna consistently found refuge in the depopulated areas.

Megafauna was able survive in the Levant until quite late in the Pleistocene, but the average size of the 83 species found at the 58 archaeological sites declined over time, and some of the larger species did eventually disappear. Elephants became extirpated in the Levant 125,000 years ago, hippos vanished here 42,000 years ago, rhinos met their demise 15,500 years ago, and the final population of the aurochs (ancestor of the domestic cow) was wiped out in the region 3500 years ago. The authors of this study believe humans preferred hunting larger animals because they provided more meat, and it took less skill to hunt them. A group of men with spears could easily bring down any large beast. Paradoxically, human hunting technology advanced when megafauna became scarce, and humans were forced to hunt smaller more elusive prey.

Reference:

Dembitzer, J. R. Borkei, M. Ben-dor, and S. Neiri

“Levantine Overkill: 1.5 million Years of Hunting Down the Body Size Distribution:

Quaternary Science Review 276 2022

Selected Plants from Jekyll Island

June 15, 2022

I encountered some interesting plants during my recent visit of Jekyll Island. Seaside oxeye (Borrichia frutescens) was a first for me, and I needed online help identifying it. This species grows in abundance on dry areas surrounding salt marshes, and it was in bloom on the island during mid-May, a little earlier than at other parts of the Atlantic coast. It belongs to the Aster family and can live for 5 years, spreading vegetatively and via seeds. The flowers attract butterflies. Leafhoppers and aphids feed upon the plant. Gall midges and gall wasps also attack the plant as part of their lifecycles. Birds eat the seeds. Seaside oxeye is reportedly an edible plant for humans and can be eaten cooked or raw, but it doesn’t have good flavor.

Seaside oxeye. This plant was blooming in abundance in the dry areas adjacent to salt marshes in mid-May on Jekyll Island.

Saltwater cordgrass (Spartina patens) is the dominant grass found in salt marshes along the North America south Atlantic coast. It is a keystone plant crucial to the health of this vital ecosystem. This plant helps maintain water quality and shelters many species of animals including diamondback terrapins, clapper rails, raccoons, otters, and fiddler crabs. Periwinkles graze on the grass to help keep it in check.

The dominant grass species growing in salt marshes along the southeastern Atlantic coast is Spartina patens. Note the dead trees. This spot is located just behind Driftwood Beach where saltwater intrusion is killing a maritime forest.

Saw palmetto (Serenoa repens) is the source of much quackery. Snake oil salesmen falsely claim extracts made from palmetto berries cure prostate problems. There is no scientific evidence for their phony claims. The palmetto berries are an edible fruit eaten by raccoons, bears, and Indians. Early European explorers were not impressed with the taste, however, and it was considered a desperation source of food. I’ve seen raccoon scat filled with palmetto berries. Saw palmetto is a scrub palm tree, and Indians used the palm fronds for fiber and roof thatching.

Saw palmetto next to a tree killed by salt water intrusion.
Live oaks here are being killed by saltwater intrusion here.

Common lantana (Lantana camara) was another first sighting for me. This species is native to Central and South America but has invaded warmer regions of North America, especially along the Atlantic coast. It is a member of the Verbena family, and its foliage is toxic to livestock. Lantana fruit, in particular the unripe berries, are highly toxic for humans, but birds relish them and spread the seeds in their droppings. This species is fire tolerant but shade intolerant and requires open landscapes to survive. The flowers come in 5 color varieties and attract butterflies and nectar feeding jumping spiders from the Salticidae family.

Lantana camara. This is a non-native species found on Jekyll Island.

Everglades Hammocks and Snails

June 8, 2022

During Pleistocene climate phases of high sea levels, the Everglades region of south Florida was flat sea bottom dotted with limestone outcrops and coral, and Lake Okeechobee was a saltwater bay. Today, the Everglades is a sea of sawgrass (Cladium jamaicense) dotted with hardwood hammocks that grow on top of the formerly inundated limestone outcrops and coral. Fresh water from Lake Okeechobee, funneled by a coastal ridge, flows south through the Everglades landscape. Sawgrass (technically a sedge not a grass) is a fire-adapted species, and during dry spells it burns, but hardwood hammocks are usually protected from the fires. Trees growing on the limestone-enriched elevated soils drop leaves, and the acidity from the decomposing leaf litter dissolves the limestone surrounding the hammock, creating moats filled with water that serve as fire breaks. Most hardwood hammocks also have an eroded solution hole in their middle, and they are elliptically shaped with 1 end pointed in the direction of the southward water flow.

Typical Everglades landscape–sawgrass wet prairie dotted with hardwood hammocks.

The composition of trees on Everglades hardwood hammocks includes a mix of tropical and temperate species. Tropical species are more common on southern Everglades hammocks, while temperate species predominate on the northern Everglades hammocks. The list of tree species found on these hammocks includes gumbo-limbo, mahogany, cocoplum, wax myrtle, live oak, red maple, hackberry, mulberry, Everglades palm, royal palm, and strangler fig.

Gumbo limbo tree. This is a tropical species common in hardwood hammocks of the southern Everglades. Everglades hardwood hammocks contain a mix of temperate and tropical species of plants.
Royal palms cannot survive frequent frost. Therefore, they are more common in the southern Everglades.

A diverse snail fauna thrives on Everglades hammocks because the limestone outcrops provide a rich source of calcium. Snails need calcium to develop their shells. The relatively frost-free climate also helps them breed year-round. Each hammock hosts a variation of tree snail (Liguus fasciatus) with a different color pattern. Over 58 variations are known. Tree snails feed upon fungus, lichen, and algae. 4 species of large apple snails live on these hammocks. 3 non-native apple snail species from South America are outcompeting the native species (Pomacea paludosa). Apple snails graze on green plant material and are a pest on south Florida vegetable farms. However, the rapidly expanding population of non-native apple snails benefit snail-eating bird species such as limpkins and the Everglades snail kite. The latter species is endangered, but the increase in snail populations has led to a rebound in Everglades kite numbers.

Native Florida apple snail. 3 species of non-native apple snails also thrive on Everglades hammocks.
Over 58 color variations of tree snails have been found on Everglades hammocks. Each hammock hosts a snail with a different color variation.
Limpkins primarily eat snails.
Endangered snail kites are increasing in population, thanks to rapidly spreading populations of non-native apple snails.

I’ve seen apple snails for sale in Asian food markets. I was not impressed with my lone snail-eating experience after I bought a can of imported escargot. They were relatively inexpensive, but they had no flavor at all. Escargots are traditionally served with butter and garlic sauce. I think eating snails is an excuse to dunk French bread in the butter and garlic sauce.

The Sand Tiger Shark (Carcharias taurus)–a Palaeocene Age Survivor

June 1, 2022

The sand tiger shark is the oldest still extant species of shark, having existed for at least 65 million years. Some sources claim it first evolved during the Cretaceous Age and lived with the dinosaurs 72 million years ago, but according to the scientific literature I can find, the oldest fossils of this species were found in the Cannonball Formation located in the Dakotas, a region that was formerly undersea, and species from fossil sites here date to the Palaeocene–the era immediately following the extinction of the dinosaurs. This is still impressive longevity for a species. By comparison modern man (Homo sapiens) has existed for about 200,000 years. The sand tiger shark should not be confused with the similarly named tiger shark (Galeocerde cuvier). Although sand tiger sharks occasionally bite people, they are not maneaters. Tiger sharks definitely are maneaters. The scientific name for sand tiger shark may also cause confusion. Carcharias taurus means bull shark in Latin, but the commonly named bull shark (Carcharhinus leucas) is also a different species.

Sand tiger shark, the oldest still extant shark species.
The sand tiger shark should not be confused with this species–the tiger shark. The former is not a maneater, but the latter is.

Sand tiger sharks can reach lengths of just over 10 feet long, and they feed upon fish, squid, and shrimp. They are known for preying on stingrays and smaller, slower sharks near the sea bottom at night. They rest during the day. They are the only species of shark to gulp air. This helps them retain buoyancy, so they don’t have to constantly swim like other kinds of sharks. The shark pups are born alive, the survivors of cannibalistic embryos attacking and eating each other while still inside their mother. Sand tiger sharks range in shallow coastal waters along the Atlantic coasts of North America and Europe. They also occur off the coasts of China, Japan, Australia, and South Africa. Scientists believe they were overfished to extinction in the Mediterranean Sea where they used to live.

Fossil sand tiger shark teeth.
Fossils from the Cannonball Formation. The majority of fossils from this site are sand tiger shark teeth. Image from the below reference.

Paleontologists found fossils of 22 species in the Cannonball Formation. This region was under ocean water until the end of the Palaeocene 55 million years ago. Sand tiger shark teeth are the most common fossil specimens found in this formation. Sand tiger sharks may be the oldest still extant species of shark, but the still extant Hexanus genus is even older. The Hexanus genus includes the gill sharks. Some species of extinct gill sharks lived 190 million years ago during the Jurassic.

Reference:

Cvancara, A.M.; and Hogansan, J.W.

“Vertebrates of the Cannonball Formation (Palaeocene) in North and South Dakota”

Journal of Vertebrate Paleontology 13 (1-23) 1993