Anomalocaris

From the start, Anomalocaris fossil was misidentified, followed by a series of misidentifications and taxonomic revisions.Anomalocaris fossils were first collected in 1886 He found abundant trilobites, along with two unknown specimens. along with 48 more of the unknown specimens. The fifty specimens were examined and described in 1892 by GSC paleontologist Joseph Frederick Whiteaves.In 1928, Danish paleontologist Kai Henriksen proposed that Tuzoia, a Burgess Shale arthropod which was known only from the carapace, represented the missing front half of Anomalocaris. In the same publication in which he named Peytoia, Walcott named Laggania, a taxon that he interpreted as a holothurian. In 1966, the Geological Survey of Canada began a comprehensive revision of the Burgess Shale fossil record, led by Cambridge University paleontologist Harry B. Whittington. Whittington linked the two species, but it took several more years for researchers to realize that the continuously juxtaposed Peytoia, Laggania and frontal appendages (Anomalocaris and "appendage F") actually represented a single group of enormous creatures. and reclassified them within different genera. In 2021, "A." saron and "A." magnabasis were reassigned to the new genus Houcaris in the family Tamisiocarididae, but subsequent analysis suggests that H. saron is a member of the family Amplectobeluidae instead and that H? magnabasis (recovered as a sister taxon of Amplectobeluidae) does not form a monophyletic clade with other species of Houcaris. In the same year, "A." pennsylvanica was reassigned to the genus Lenisicaris. In 2022, specimen ELRC 20001 that was treated as an unnamed species of Anomalocaris or whole-body specimen of A. saron got a new genus, Innovatiocaris. In 2023, "A". kunmingensis was reassigned to the new genus Guanshancaris in the family Amplectobeluidae. Multiple phylogenetic analyses also suggested that "A". briggsi (tamisiocaridid) was not a species of Anomalocaris either, and it was reassigned to the genus Echidnacaris in the family Tamisiocarididae in 2023. Radiodonts like Anomalocaris are recognised as early diverging relatives of modern arthropods, sharing key morphological features such as bearing segmented frontal appendages and compound eyes, but also lacking key features of modern arthropods (Deuteropoda), such as lacking segmented two-branched (biramous) trunk limbs. Cladogram after Liu et al. 2026: }}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}}|label1=Panarthropoda|style=font-size:90%}} == Description ==

Anomalocaris was gigantic in comparison to contemporary animals. A complete specimen of A. canadensis, ROMIP 51211, is measured up to long and this overlapping allowed the lobes on each side of the body to act as a single "fin", maximizing the swimming efficiency. The construction of a remote-controlled model showed this mode of swimming to be intrinsically stable, implying that Anomalocaris would not have needed a complex brain to manage balance while swimming. The body was widest between the third and fifth lobe and narrowed towards the tail, with additional three pairs of small flaps on the constricted neck region. Anomalocaris 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. The top one, known as a head shield, dorsal carapace or H-element, was shaped like a laterally-elongated oval, with a distinct rim on the outer edge. the resolution of the eyes would have been rivalled only by that of the modern dragonfly, which has 28,000 lenses in each eye. Additionally, estimation of ecdysozoan opsins suggest that Anomalocaris may have had dichromatic color vision. The tail was a large tail fan, composed of three 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. == Paleobiology ==

The interpretation of Anomalocaris as an active predator is widely accepted throughout the history of research, In the case of A. canadensis, its outstanding size amongst Burgess Shale fauna also make it one of the first apex predators known to exist. Some Cambrian trilobites have been found with round or W-shaped "bite" marks, which were identified as being the same shape as the mouthparts of Peytoia (previously misidentified as those of Anomalocaris The lack of wear on radiodont mouthparts suggests they did not come into regular contact with mineralized trilobite shells, and were possibly better suited to feeding on smaller, soft-bodied organisms by suction, since they would have experienced structural failure if they were used against the armour of trilobites. Three-dimensional modelling of various radiodont frontal appendages also suggest that A. canadensis is more capable to prey on smaller ( in diameter), active, soft-bodied animals (e.g. vetulicolian; free-swimming arthropods like isoxyids and hymenocarines; Nectocaris). == Paleoecology ==

Specimens of Anomalocaris have been found worldwide spanning from Cambrian Stage 3 to the Guzhangian. Aside from the Burgess Shale and Emu Bay Shale, fossils have been found in the Chengjiang Biota, Hongjingshao Formation, Balang Formation and the Kaili Formation of China, as well as the Eagar Formation and Weeks Formation in the United States. In the Burgess Shale, Anomalocaris is more common in the older sections, notably the Mount Stephen trilobite beds. However, in the younger sections, such as the Phyllopod bed, Anomalocaris could reach much greater sizes—roughly twice the size of its older, trilobite bed relatives. These rare giant specimens have previously been referred to a separate species, Anomalocaris gigantea; however, the validity of this species has been called into question, in what is now modern China. Anomalocaris daleyae (Emu Bay Shale) lived in a comparable environment; the shallow, tropical waters of Cambrian Australia. which are no longer considered species of Anomalocaris. == See also ==