76. Review of Animal Paradise figurines: ancient sea creatures
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Cephalaspis is a genus of extinct marine jawless agnathans from the family Cephalaspidae, order Cephalaspiformes, or bony shields. They lived in the Upper Silurian to Middle Devonian (427.4–382.7 million years ago). Cephalaspis is one of the first discovered ostracoderms. Characteristic features of the genus include a fairly long preorbital portion of the cephalic shield, a parabolic shape of the shield margin, and a narrow median field of small bony plates. Animals of this genus reached 60 cm in length and were covered anteriorly by a massive carapace, which served as protection from predators but significantly reduced mobility. However, they had well-developed muscles in the flexible rear portion of their bodies and, unlike most ostracoderms, pectoral fins.
Cephalaspis lacked jaws and likely fed on bottom detritus on coral reefs. In turn, they served as food for large predators, such as eurypterids and placoderms.
Anomalocaris is a genus of fossil arthropods from the class Dinocarida. They lived in the seas and used flexible lateral lobes for swimming. They were among the largest organisms known from Cambrian deposits: body length could reach 60 cm. They have been described from deposits in North America, China, and Australia, dating back 520–505 million years.
Ancient Anomalocaris possessed excellent vision, provided by a pair of compound eyes. The visual acuity of Anomalocaris is provided by at least 16,000 hexagonal lenses. The presence of such complex eyes in Anomalocaris suggests that compound vision began to develop in arthropods much earlier than previously thought. Remarkably, the visual acuity of the ancient Anomalocaris likely surpassed many of its modern relatives. For comparison, a fly's eye has about 4,000 lenses, while an ant's eye has about 100.
Orthoceras, or Orthocerata, is a genus of extinct cephalopod mollusks. They lived during the Ordovician period and became extinct at the end of the Triassic period. Like nautiluses and ammonites, Orthocerata had a large, well-developed shell, but unlike them, Orthocerata's shell was conical rather than spiral. When threatened, Orthocerata could hide its head and tentacles within the shell. The head of the Orthocerata had large eyes and numerous tentacles. Like modern nautiluses, Orthocerata lacked suckers on their tentacles. They used their tentacles to capture their prey (various small animals) and pull it toward their mouth, which housed a strong beak.
Their massive, straight shell likely created certain difficulties for Orthocerata when swimming and especially when maneuvering. Because of this, they primarily lived near the seafloor, moving slowly in search of prey.
Opabinia is a genus of extinct animals known from fossil remains found in Cambrian deposits (approximately 508 million years old).
Thirty specimens of Opabinia, ranging in size from 40 to 70 mm, are currently known. Opabinia's most notable feature is its five eyes, located on the back of its head. These eyes were likely used to locate food. Its flexible body makes it unclear whether Opabinia led a pelagic or benthic lifestyle.
Trilobites are a class of extinct marine arthropods that were of great importance to the fauna of Paleozoic formations around the globe. Over 10,000 fossil species and 5,000 genera are known, grouped into 150 families and 9-10 orders.
According to one theory, the ancestor of trilobites was Spriggina, a late Proterozoic organism about 3 cm long.
The body structure of trilobites bears evidence of adaptation to a bottom-dwelling lifestyle: a thick shell (exoskeleton), flattened form, compound eyes on the dorsal side of the body, and the mouth and legs located on the ventral side of the body. Trilobites reached body lengths of up to 72 cm, and even up to 90 cm. Some groups of trilobites fed on mud, others on small invertebrates, and still others on plankton. Many trilobites had the ability to curl up their bodies like woodlice, so that the entire soft body was trapped under the shell. This curling served as protection from larger predators.
Eurypterids, also known as sea scorpions, or eurypterids are a group of fossil arthropods from the class Merostomata, subphylum Chelicerata, comprising approximately 250 known species. Some representatives reached 2 meters in length, but the typical size of most species did not exceed 20 cm. They existed throughout the Paleozoic Era, from 510 to 248 million years ago. Early forms inhabited shallow seas. Around 325 to 299 million years ago, most transitioned to freshwater life. The evolution of eurypterids clearly demonstrates the transition from an aquatic to a terrestrial lifestyle. The biology of eurypterids is particularly suggestive of a carnivorous lifestyle. Not only were many of them large (as most predators are larger than their prey), but they also possessed stereoscopic vision (the ability to perceive depth).