STL Science Center

STL Science Center

18 January 2018

The Popular Shrimp

In case anyone did not realize how popular Anomalocaris is, after all of the documentaries (minor and major) and different books, texts, robots, and multiple illustrations and photos of the Cambrian's largest predator, here is a picture I took Monday afternoon at Michael's, a hobby and craft store:
Though the eyes were not colored in like compound eyes, we can see that they do still feature prominently on this version of Anomalocaris. Toys are not the ultimate models of fossil animals, though this toy Anomalocaris does look a lot like a number of the good museum models that exist across the world. As an example, here are models from the National Dinosaur Museum in Canberra, Australia (left) and the Houston Museum of Natural Science (right).
Photo by Yinan Chen; CC0 1.0 Universal (CC0 1.0)
Photo by Photnart; CC0 1.0 Universal (CC0 1.0)















Perhaps, however, the ultimate popular culture manifestation of the admiration and love of Anomalocaris might just be this plush version of our favorite ocean going arthropod. I have to say that it honestly looks a little bit more fluffy and adorable than it does frightening and carnivorous.

17 January 2018

Mouths and Arms

James St. John - (Burgess Shale Formation, Middle Cambrian;
Walcott Quarry, above Field, British Columbia, Canada)
The grasping appendage, sometimes called an arm, of Anomalocaris was approximately 45.72 cm (18 in) long and covered in spiky barbs. The arms and the spiky barbs would have served two important uses in the feeding behavior of the Cambrian predator: 1) to grasp and hold prey items and 2) to move the food near and into the mouth of Anomalocaris. These long grasping appendages, in coordination, with the large compound eyes made Anomalocaris an accurate predator, though of course we do not have any way to gauge its actual capture rate. Dragonflies, in the world of extent arthropods, are the most successful hunters with a prey capture rate that is approximately 95%. The current apex predators of the ocean, Great White Sharks and Orcas, have widely variable hunting success rates that are reported between 48% (for Great White Sharks) and 95% (for Orcas). Anomalocaris could have fallen anywhere in this range, but was most likely fairly successful given its high mobility, articulate (appearing) arms, and compound eyes. The mouth, of course, had quite an impact on the feeding capabilities of Anomalocaris as well.
James St. John - Anomalocaris canadensis mouthpiece
(~5.25 x ~4.25 cm) from the Walcott Quarry, Burgess Shale

The mouth of Anomalocaris consisted of 32 oral plates that have, multiple times, been compared to pineapple rings. The plates were constituted of 4 large and 28 small interlocking plates that were ringed internally by denticulate prongs that, thanks to multiple specimens, have been observed stretching down the entire gullet of the animal. This ring, save where the denticulate prongs would meet or occlude, was capable of closing and crushing, effectively biting in a circular motion, the trilobites that it shared the Cambrian waters with.

16 January 2018

A Few Good Papers

There are numerous papers on trilobite wounds and feeding in the Cambrian sea as inferred from ichnofossils and taphonomic studies (as a singular example consider Selly, et al. 2015). Many of these address the mouth and feeding appendages of Anomalocaris; however, before considering how the animal was capable of biting and wounding prey or grasping its prey and pulling it toward its mouth, one needs to understand how all of the elements of Anomalocaris anatomy come together. Descriptions of the animal can be found in many different places, but one of the more intense versions of a description of Anomalocaris is Whittington and Briggs, 1985. The authors describe not only the genus Anomalocaris in great detail, but also the general stratigraphic surroundings of all known (at the time) specimens of Anomalocaris and each species in greater detail including the holotypes and any referred material then known. As a comprehensive description for understanding the species this paper is a must read. However, it is a highly detailed scientific paper, and it can therefore be a difficult read as well. One of the first portions of the 40 page article is a terminology section which should help non-scientist readers, arguably. If reading through an article of this length is not for you today, though, popular science articles like Briggs 1994 (includes discussion of a robotic model used to analyze swimming in Anomalocaris), Patterson, et al., 2011 (previously mentioned discussing compound eyes), and Nedin 1999 (for more discussion about the mouth and feeding in Anomalocaris).

15 January 2018

Anomalocaris on Tape

The way of the on-tape documentary has gone, so saying that Anomalocaris is more well known from its appearance on a taped documentary is not entirely correct, though it is certainly where most know the name and general shape of the Cambrian animal Anomalocaris. Despite existing entirely as a 3D digital model in underwater scenes of the first episode of the Walking with Series in which it appears, Anomalocaris has made a lasting impression in the minds of paleontologists, people afraid of creepy sea creatures, and most likely some impressionable youngsters that just like documentaries about odd creatures. Anomalocaris has appeared in other documentaries as well, but its general model is the same. Regardless of which documentary we watch, Anomalocaris is depicted as a very active predatory arthropod. Anomalocaris was capable of breaking into the hardened shells protecting the bodies of its prey items, such as the trilobites shown in this documentary clip. A general overview of Anomalocaris is also available, in a separate and previously unknown, to me, documentary that lasts approximately 11 minutes. This is the direct link shared below:

14 January 2018

Largest Facts of the Burgess Shale

The largest known animal of the Burgess Shale is Anomalocaris and this undisputed fact is often the first fact mentioned on any site that discusses the facts we know about this (as the Smithsonian calls it) proto-arthropod. The scale shared yesterday considers the largest known specimens of the genus; however, related and possible members of the genus recovered from China approach 1.8 m (6 ft) long. The scale on Prehistoric Wildlife's page detailing Anomalocaris does show what a nearly 6 foot animal would look like compared to an average human. The page also has a rather extensive list of suggested reading; this constitutes a good source of papers for getting ahead of those papers that will be shared on Tuesday. The page also contains a rather extensive description of the history of the animal's discovery and description of Anomalocaris.

The best image of Anomalocaris on a fact page is probably the illustration on DKfindout's encyclopedia page, though the page itself does not share as much detailed information as either the Smithsonian or Prehistoric Wildlife pages. This illustration makes the eyes of Anomalocaris very obvious, though the page does not directly address the interesting optic organs. Luckily, though, scientists have noticed that this Cambrian predator (or potential filter feeder) has well developed eyes. Discover Magazine's Ed Yong authored an article just over 6 years ago wrote a scientific journalism article detailing the first detailed discovery and description of Anomalocaris eyes by John Paterson of the University of New England (in Australia, not the northeastern United States). Doctor Paterson discovered, in a massive number of Anomalocaris fossils from southern Australia's Emu Bay Shale deposits, a pair of sophisticated compound eyes containing an estimated 16,700 lenses on the best preserved surface; estimations of total eye coverage may be discussed later this week providing I can find such information.

13 January 2018

Welcome Back to Crazy Animals

©Dinoguy2 CC BY-SA 3.0
Coming back from a short hiatus and a very long Twitter feed at a scientific conference, this blog is ready to talk fossils and extinct animals again. We are going to go back pretty far into the fossil record for this first week back too. As I stated in the name change post, we are expanding our view beyond dinosaurs alone and even further than we ever have in the past (such as mammals and amphibians). To start looking at how massive the fossil record truly is, we will relaunch this week looking at one of the earliest known large sea creatures, an arthropod genus known as the "Abnormal Shrimp"; Anomalocaris. Some may recognize the name from the documentary series Walking with Prehistoric Monsters, the final series in the Walking with series of documentaries. Known largely from deposits of the Burgess Shale and other shales such as the Ogygopsis Shale (a subseries of the Burgess Shale), Anomalocaris consists of two accepted species and a third more contentious species. The original fossils, dating from 1892, consisted of a deceptively separated "arm", now known to be an individual portion of the feeding appendages encased in Middle Cambrian (508 MA) shales. The fragmentary nature of many specimens of Anomalocaris have, in the past, led to this single type of animal being labeled as many different animals and different types of animals. The body consists of many lobes and, as with all arthropods, these lobes are covered in a mineralized shell. The frightening look of this multi-lobed, shelled animal may be more a remnant of its alien (to us) body plan than it was an actually frightening carnivorous animal. One of the three species appears to have possessed robust feeding appendages capable of piercing the shells of other animals of the Cambrian sea; however, the other two species do not possess these and the diet of these other two species has been hypothesized to have been filter feeding rather than carnivory. Multiple dietary preferences in this genus point to a much more diverse group than has been portrayed in common accounts and means that the animal we are going to discuss this week is much more complex than originally thought as well.

06 January 2018

SICB Twitter Feed

Dear readers, I apologize for not having written earlier, but I've been far busier than I assumed I would be. Below find the Twitter feed of SICB material I promised. I may need to edit the code later, but that's easier on a laptop, and I am on my phone right now!