Ecological stasis in Spinicaudata (Crustacea, Branchiopoda)? Early Cretaceous clam shrimp of the Yixian Formation of north‐east China occupied a broader realized ecological niche than extant members of the group

Abstract

The palaeoecology of Spinicaudata, the dominant group of benthic invertebrates in many pre‐Cenozoic freshwater environments, remains poorly understood. In analogy with extant taxa, it has been oversimplified and often reduced to shallow, temporary environments characterized by few trophic levels, implying ecological stasis from the Devonian to the Recent. We excavated 43 horizons of the Lower Cretaceous Yixian Formation (Anjiagou and Hengdaozi beds) to evaluate whether spinicaudatan ecology can be simplified to such an extent. Sedimentological evidence suggests general perennial conditions during the excavated lake interval. Based on 33 226 specimen counts, we identified three arthropod‐dominated macrobenthic associations and two assemblages. Response curves indicate that the spinicaudatan Eosestheria middendorfii was exceptionally tolerant to environmental gradients, followed, in decreasing order, by mayfly larvae, water boatmen and oligochaetes. Many spinicaudatan‐yielding layers represent death after reproductive senescence rather than mass‐mortality events. Spinicaudatan size varies significantly according to faunal association. A forward stepwise regression model suggests that growth responded to population density and diversity: lower densities and higher diversities triggered fast growth, and vice versa. The proposed strong density effect on carapace size has been corroborated by rearing experiments: as for E. middendorfii, natural log regression provided the best fit for the two extant species Eulimnadia texana and Eocyzicus argillaquus. Hence, E. middendorfii was a tolerant and morphologically variable species adapted to perennial waters and the frequent presence of higher trophic levels. Although there are rare records of extant taxa co‐occurring with fish, the described Early Cretaceous environment is commonly not inhabited by extant Spinicaudata.

Disaster microconchids from the uppermost Permian and Lower Triassic lacustrine strata of the Cis-Urals and the Tunguska and Kuznetsk basins (Russia)

“…These organisms are preserved in the Petropavlovka Formation either as body fossilsostracods, spinicaudatans and a microdrile (Tverdokhlebov, 1967;Shcherbakov et al 2019Shcherbakov et al , 2020 or, in the case of dipnoan fish, as both body and trace fossils (Minikh & Minikh, 1997;Sennikov, 2018). Common spinicaudatants and sparse horseshoe crabs of the Petropavlovka Lagerstätte also typified Mesozoic freshwater communities (Lamsdell, 2016;Hethke et al 2019),…”

Palaeoenvironmental reconstruction and biostratinomic analysis of the Jurassic Yanliao Lagerstätte in northeastern China

“…The aquatic ecosystem of the lake(s) resembled that of modern short-lived waterbodies, including a low-diversity aquatic fauna and high density of monospecific assemblages, dominated by crustaceans and pond-type salamanders (Vannier et al, 2003;Liu et al, 2010;Sullivan et al, 2014). In particular, clam shrimps yield dormant eggs that may rapidly hatch after several years (to decades) of drought (Dumont and Negrea, 2002) or without prior desiccation (Bishop, 1967;Hethke et al, submitted). Hence, they disperse through water-, animal-and wind transportation (Tasch, 1969;Webb, 1979;Frank, 1988), and might have easily endured frequent collapses of the lacustrine ecosystem caused by volcanic eruptions.…”

“…However the longevity of the lake(s) remains uncertain as ecological comparison between these benthic aquatic taxa of the Haifanggou Formation and their modern relatives is inconclusive. Although clam shrimp population palaeoecology has often been interpreted based on an analogy with extant "shallow and temporary" habitats (e.g., Webb, 1979;Frank, 1988;Vannier et al, 2003;Olempska, 2004), their Mesozoic analogues clearly occupied a much wider ecological space (Olsen, 2016;Hethke et al, submitted). In addition, modern Corixidae can be early colonizers of temporary waters, but many species frequently appear in permanent ponds and lakes as well as streams (e.g.…”

The complete mitogenome of an undescribed clam shrimp of the genus Gondwanalimnadia (Branchiopoda: Spinicaudata), from a temporary wetland in Central District, Botswana

“…Similar to other branchiopods, clam shrimp rapidly attain sexual maturity and within short hydroperiod windows, produce dormant eggs that can withstand dry periods (Brendonck et al 2008;Rogers 2009). They are thought to be omnivores with diets consisting of detritus, plankton and algae (Hethke et al 2019). Gondwanalimnadia spp.…”

“…They are thought to be omnivores with diets consisting of detritus, plankton and algae (Hethke et al. 2019 ). Gondwanalimnadia spp.…”