A Cambrian Wolf, a Cambrian Smilodon, a Cambrian Dimetrodon.

Greetings. An apex predator existed 520 million years ago, a wolf, a smilodon, a dimetrodon by any other name. Known as Anomalocaris, these extinct predators were members of an extinct genus of radiodont, an order of early-diverging stem-group marine arthropods. The genus' best known species is Anomalocaris canadensis, known from fossilized remains found in British Columbia, Canada. 

Like other radiodonts, Anomalocaris canadensis had swimming flaps running along the entire length of its flexible body, large compound eyes, and a single pair of segmented, frontal appendages, which were used to grasp and dispatch prey. Estimated to reach 37.8 centimeters long excluding the frontal appendages and distinctive tail fan, A. canadensis was one of the largest animals of the Cambrian Period, and thought by paleontologists to be the earliest example of an apex predator. 

Remains of Anomalocaris canadensis were first collected in 1886 by Richard G. McConnell of the Geological Survey of Canada (GSC.) Having been informed of rich fossils at the Stephen Formation in British Columbia, McConnell climbed Mount Stephen on the 13th of September 1886. He found abundant trilobites, along with two previously unknown specimens. By August of 1891, Henri-Marc Ami, an Assistant Palaeontologist at GSC, collected more trilobites and brachiopod fossils, along with 48 more of the unknown specimens. The fifty unidentified specimens were eventually examined and described in 1892 by GSC paleontologist Joseph Frederick Whiteaves. Whiteaves interpreted them as the abdomens of phyllocarid crustaceans, and gave the full scientific name Anomalocaris canadensis. 

Anomalocaris canadensis propelled itself through the waters of the Cambrian by undulating the flexible flaps on the sides of its body. Each flap sloped below the one more posterior to it, this overlapping allowing the lobes on each side of the body to act as a single "fin," maximizing the efficiency of the animal's efforts. The animal's body was widest between the third and fifth lobe and narrowed towards the tail, with an additional three pairs of small flaps on the constricted neck region. 

Anomalocaris canadensis had an unusual disk-like mouth known as an oral cone. The oral cone was composed of several plates organized triradially. Three of the plates were quite large. Three to four medium sized plates could be found between each of the large plates, and several small plates between them. Most of the plates wrinkled and have scale-like tubercles near the mouth opening. Such an oral cone is very different from those of a typical hurdiid radiodont like Peytoia and Hurdia, which is smooth and tetraradial. As a shared character across radiodonts, Anomalocaris also had three sclerites on the top and side of its head. The top one, known as a head shield, was shaped like a laterally-elongated oval, with a distinct rim on the outer edge.

Two large frontal appendages were positioned in front of the mouth, at the front of the head. Each frontal appendage usually had 14 podomeres (segmental units, at least 1 for shaft and 13 for distal articulated region,) with each appendage being laterally-flattened, somewhat taller than wide. Most podomeres were tipped with a pair of ventral spines. The endites themselves were both equipped with multiple auxiliary spines, which branches off from the anterior and posterior margin of the endites. The tail of A. canadensis was a robust structure, composed of three pairs of large, lateral fin-shaped lobes and one terminal lobe-like tailpiece. The gills of the animal, in the form of long, thin, hair-like structures known as lanceolate blades, were arranged in rows forming setal blades. The setal blades were attached by their margin to the top side of the animal, two setal blades per body segment. A divide ran down the middle, separating the gills. The stalked eyes of A. canadensis were 30 times more powerful than those of trilobites, long thought to have had the most advanced eyes of any contemporary species. With one specimen having over 24,000 lenses in one eye, the resolution of the 3 centimeter wide eyes would have been rivalled only by that of the modern dragonfly, which has approximately 28,000 lenses in each eye. Additionally, A. canadensis may have had dichromatic color vision.

Anomalocaris canadensis, a wolf, a smilodon, a dimetrodon by any other name.

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