The oldest hyolithids (Cambrian Series 2, Montezuman Stage) from the Iapetan margin of Laurentia

Abstract

The recent description of the nevadioid trilobite Buenellus chilhoweensis Webster and Hageman, 2018 established the presence of early Cambrian Montezuman Stage (Cambrian Series 2, Stage 3) faunas in the Murray Shale of Chilhowee Mountain, Tennessee. The description recognized the oldest known age-diagnostic Cambrian trilobite from the Laurentian margin of the former Iapetus Ocean since Buenellus Blaker, 1988 is known otherwise only from the Sirius Passet Lagerstätte on the Innuitian margin of North Greenland. The bivalved arthropods Isoxys chilhoweanus Walcott, 1890 and Indota tennesseensis (Resser, 1938a) have also been described from the Murray Shale, but hyolithids appear to be the dominant body fossils in terms of diversity and abundance. Although poorly preserved, the hyolithids occurring together with Buenellus chilhoweensis are described to improve understanding of the Murray Shale biota. The hyolith assemblages of the Murray Shale and Sirius Passet Lagerstätte are not closely similar, although the poor preservation of both hinders comparison.

Thecate stem medusozoans (Cnidaria) from the early Cambrian Chengjiang biota

“…Besides the descriptions above, some other species in Burithes also have the following features (Peel et al . 2020): (1) ventral side of the aperture has a ligula that in length measures about one‐sixth of the conch's length, and in width measures about half of its length; (2) ventral surface has periodic, co‐marginal growth lines with occasional halts; (3) the ventral side has Y‐shaped cracks that extend from the ligula margin down the median line, probably a taphonomic artefact. Also, Malinky et al .…”

Morphological disparity and evolutionary patterns of Cambrian hyoliths

“…The high abundance of hyoliths during the Cambrian makes them one of the more important components of the Cambrian evolutionary fauna (Sepkoski 1981), with hyoliths frequently recovered from early and middle Cambrian deposits. The majority of recent hyolith studies have focused on their occurrence (Pan et al 2019;Peel et al 2020;Liu et al 2021aLiu et al , 2021bLiu et al , 2022b, biological affinities (Moysiuk et al 2017;Sun et al 2018a;Li et al 2019;Liu et al 2020) and palaeoecology (Kimmig & Pratt 2018;Sun et al 2018bSun et al , 2019Liu et al 2021a), which have all served to expand understanding of both hyolith biodiversity and distribution. Despite their known importance, studies of hyolith evolution are scarce, with little comparative work or broad-scale analysis of the evolutionary trajectory of hyoliths during the Cambrian.…”