Rhynchonelliformean Brachiopods With Soft‐tissue Preservation From the Early Cambrian Chengjiang Lagerstätte of South China

Abstract

Cosmopolitan kutorginates, the most abundant Early Cambrian rhynchonelliformean brachiopods, became extinct at the end of the Middle Cambrian. Consequently, any information concerning the anatomy of this peculiar lineage of brachiopods has great phylogenetic significance with regard to their extant relatives for analogies with the stem-group clade. Such data have been supplied from fossils of which the soft parts have been preserved in exceptional detail. A new brachiopod, Kutorgina chengjiangensis sp. nov., from the Early Cambrian Chengjiang Lagerstätte of southern China, is described here. It is the first articulated brachiopod species collected from this deposit. The specimens preserve a set of soft-body parts, i.e. lophophore, digestive tract and pedicle, all previously poorly known in almost all Palaeozoic calcareous brachiopod taxa. The lophophore attains an early spirolophe stage, clearly homologous to that in the coeval lingulids. The digestive tract consists of a mouth, oesophagus, swollen stomach, intestine and a terminal anus. The pedicle protruding between the valves is stout and elongate, with annulated lamellae on the surface, and contains a putative coelomic cavity. K. chengjiangensis displays the characteristics of the stem group of calcareous brachiopods, and illustrates anatomical similarities between Cambrian phosphatic-and calcareous-shelled brachiopods, thus corroborating that the Brachiopoda are a monophyletic group.

Depth related brachiopod faunas from the lower Cambrian Forteau Formation of southern Labrador and western Newfoundland, Canada

“…Although many taxa have long pedicles, present evidence suggests that few Cambrian brachiopods were infaunal like the Recent Lingula Bruguière, 1791 (see discussion in Bassett et al, 1999, Zhang et al, 2008and Topper et al, 2015, although rare burrowing traces of probable linguliform brachiopods have been described from sandstones with abundant Skolithos burrows of the Bradore Formation of southern Labrador (Pemberton and Kobluk, 1978). The general pattern from studies of brachiopods from Cambrian lagerstätten is that most taxa appear to be epifaunal suspension feeders (Bassett et al, 1999) that attached directly to the seafloor, to dead shells or living members of the benthos such as algae, sponges, chancelloriids, or even other brachiopods (Mergl, 2002;Caron, 2006;Zhang et al, 2004Zhang et al, , 2007Zhang et al, , 2008Zhang et al, , 2010Zhang et al, , 2011Topper et al, 2015). Burrowing lifestyles among brachiopods in the Cambrian were likely restricted to nearshore arkosic environments.…”

“…New information on the autecology of Cambrian brachiopods has recently come from studies on brachiopods with preserved soft parts (Zhang et al, 2004;2009, 2011Petterson Stolk et al, 2009) and the physical association of brachiopods with other organisms (Holmer and Caron, 2006;Zhang et al, 2007Zhang et al, , 2010Topper et al, 2014Topper et al, , 2015 in the Chengjiang and Burgess Shale lagerstätten. Although many taxa have long pedicles, present evidence suggests that few Cambrian brachiopods were infaunal like the Recent Lingula Bruguière, 1791 (see discussion in Bassett et al, 1999, Zhang et al, 2008and Topper et al, 2015, although rare burrowing traces of probable linguliform brachiopods have been described from sandstones with abundant Skolithos burrows of the Bradore Formation of southern Labrador (Pemberton and Kobluk, 1978).…”

“…Their utility for biostratigraphy and biogeography is hampered, however, because early Cambrian brachiopods remain poorly understood in terms of their ecology. Exceptionally preserved brachiopods exhibiting details of soft anatomy, in particular from the Chengjiang fauna of south China (Zhang et al, 2004(Zhang et al, , 2007(Zhang et al, , 2008(Zhang et al, , 2009(Zhang et al, , 2010(Zhang et al, , 2011 and the Burgess Shale (Holmer and Caron, 2006;Petterson Stolk et al, 2009;Topper et al, 2014Topper et al, , 2015 have recently yielded important insight into the autecology of early Cambrian brachiopods, but unfortunately the vast majority of described taxa have not been found in these exceptional faunas.…”

Epibionts on the lingulate brachiopod Diandongia from the Early Cambrian Chengjiang Lagerstätte, South China

“…To date, more than 400 specimens of the botsfordiid D. pista have been collected from the yellowish-green or greyish-green mudstone of the Chengjiang Lagerstätte at more than 10 localities around Kunming (Zhang et al 2007b). The strata containing the Chengjiang fauna belongs to the Yu'anshan member (Eoredlichia zone) of the Lower Cambrian Heilinpu Formation (Luo et al 1999).…”

“…In the Chengjiang brachiopod assemblage, the brachiopod Xianshanella haikouensis (Zhang et al 2006) tended to elevate its feeding structure through its elongated pedicle to the highest possible level above the sea bottom; this upper biotope level was also occupied by the epibenthic, fixosessile L. chengjiangensis ( Hou et al 1999) and Kutorgina chengjiangensis (Zhang et al 2007b). Then we might surmise that D. pista (Rong 1974;Zhang et al 2003Zhang et al , 2008 and H. orienta ( Jin & Wang 1992) could have occupied the lowest ecological niche near the sediment-water interface, as evidenced by the overgrowth with its epibionts.…”