Triamyxa coprolithica, Qvarnström & Fikáček & Vikberg Wernström & Huld & Beutel & Arriaga-Varela & Ahlberg & Niedźwiedzki, 2021

Qvarnström, Martin, Fikáček, Martin, Vikberg Wernström, Joel, Huld, Sigrid, Beutel, Rolf G., Arriaga-Varela, Emmanuel, Ahlberg, Per E. & Niedźwiedzki, Grzegorz, 2021, Exceptionally preserved beetles in a Triassic coprolite of putative dinosauriform origin, Current Biology 31, pp. 1-8 : 5

T. coprolithica sp. nov.

Type material

Holotype: complete specimen ( Figures 1B–1D ) preserved in coprolite ZPAL AbIII/3520 , stored at the Institute of Paleobiology, Polish Academy of Sciences (Warsaw). Paratypes: one complete and 13 partly to totally disarticulated specimens in the same coprolite ( Figures 1E–1G and 1I ). The publication is registered in ZooBank: http://zoobank.org/ urn:lsid:zoobank.org:pub:6, to describe the new species as a valid taxon.

Type locality and horizon

Krasiejów clay pit , near Ozimek, Upper Silesia, Poland. The material from the upper bonebed, part of the Keuper succession from Silesia, can be correlated with the Drawno Beds. Biostratigraphic data support a late Carnian age of the Krasiejów biota.

Diagnosis

Body length 1.4–1.7 mm, elytra 0.9–1.3 mm long and 0.4–0.5 mm wide. Body elongate navicular ( Figure 1F ). Diagnostic characters asfor the family. Adetailed description of the new species is provided in STAR Methods.

Description of Triamyxa coprolithica gen. & sp. nov

Body length 1.4–1.7 mm, elytra 0.9–1.3 mm long and 0.4–0.5 mm wide. Body elongate, navicular, slightly compressed dorsolaterally. Head. ca. as long as wide, gradually narrowing behind eyes, strongly narrowed and slightly prolonged in front of eyes. Anterior margin of head (?labrum) subquadrate. Genal folds not developed, and hence mandibles visible laterally. Compound eyes large, strongly protruding laterally. Mentum transverse, with its posterior margin reaching slightly anteriad of mid-length of eyes, anterior margins weakly rounded. Maxillary stipes elongate. Maxillary palpi elongate; penultimate maxillary palpomere slender, slightly shorter than terminal one; terminal palpomere long and slender, fusiform. Antennae inserted dorsally in a depressed area of frons between eyes; scapus large, elongate, pedicel shorter; apical portion of antenna with slightly enlarged antennomeres, apparently forming a slightly widened antennal club. Number of antennomeres uncertain, but probably 9 as suggested by available reconstructions: scape, pedicel, 4 intermediate antennomeres and 3 antennomeres of the antennal club. Prothorax. Pronotum strongly narrowing anteriad, anterolateral corners strongly projecting; posterolateral corners subacute; posterior margin strongly projecting posteriad, likely covering scutellar shield; dorsal disc evenly arcuate, without distinct grooves or ridges; ventral hypomeral portion of pronotum separated from dorsal disc by distinct edge, rather narrow, posteromesally projecting as a small tooth. Prosternum in front of procoxae long, anteriorly possibly in narrow contact with pronotum; its mesal portion slightly raised; posteromesally projecting as very short and rounded prosternal process. Propleuron present and exposed, drop-shaped (it may or may not reach anterior margin of prothorax, reconstruction of this region is ambiguous). Procoxal cavities closed internally and widely open externally along entire posterior margin. Mesothorax slightly shorter than metathorax on ventral side. Mesoventrite with wide subpentagonal elevation posteriorly broadly meeting metaventrite; laterally bordering anterior margin of very widely separated mesocoxal cavities; likely at least partly separated from mesanepisternum, wide anteriorly, with anapleural sutures slightly diverging posteriorly. Mesocoxal cavities rounded, very widely separated from each other, completely bordered by meso- and metaventrite. Elytra long, dorsally covering complete abdomen except for last one or two segments (see below); elytral apex truncate; elytral epipleura likely reaching level of metathorax. Metathorax wider than long on ventral side, anteromesally with a wide projection meeting mesoventral elevation. Metanepisternum moderately wide. Metacocal cavities transverse, reaching lateral border of metaventrite but not elytral epipleura. Abdomen with 5–6 exposed ventrites (since specimens with both 5 and 6 ventrites are present in the material examined, we conclude that either the 6 th ventrite is highly movable and may be either totally retracted or largely protracted, or alternatively that the morphology of the abdomen is sexually dimorphic, with females with 5 ventrites and males with 6 ventrites). Ventrite very long, extensive, with narrow intercoxal projection; ventrite 2 slightly more than half as long as 1, 3 slightly shorter than 2, and 4 slightly shorter than 3; ventrite 5 parabolic, with evenly rounded posterior margin; ventrite 6 (if present) narrow and very elongate; all segments with tergites separated from sternites by lateral membrane, no abdominal segment entire and conical. One specimen with 6 ventrites apparently displays a slightly protruding, narrow rod-like aedeagus. Legs. Pro- and mesocoxa subglobular; metaxoca transverse, with narrow plates partly covering metafemora and basal portion of proximal abdominal ventrite. Trochanters of all legs small. Femora narrow and elongate, with tips reaching or slightly overtopping body outline; mesofemur narrow basally, widened distally. Tibiae slender, slightly bent inward. Tarsi short, very likely with relatively long terminal tarsomere, but subdivision and number of tarsomeres not clearly preserved; all tarsi with a pair of massive claws.

Thelocality

The Upper Triassic section at Krasiejów in Poland presents an almost 30-m thick succession with variegated mudstones and thin lenses of calcareous grainstones. Two main fossil-bearing intervals comprise remains of both lacustrine and terrestrial. 23 The latter consists of a large predatory rauisuchian ( Polonosuchus silesiacus), an aetosaur ( Stagonolepis olenkae), a dinosauriform ( Silesaurus opolensis), an archosauromorph (Ozimek volans), and varioussmall other diapsids. 23, 44 Thefreshwater fauna includes temnospondyls ( Metoposaurus krasiejovensis and Cyclotosaurus intermedius), a large phytosaur ( Parasuchus sp. ), actinopterygians, a hybodont ( Lonchidion sp. ) and various invertebrates. 23, 44 Alate Carnian age of the fossil assemblage is inferred from plant macrofossils, the vertebrate community, conchostracans, and charophytes, 23, 45 – 49 since there are no radiometric dates from the succession.

Figures

Figure 1. Contents of coprolite fragment ZPAL AbIII/3520 (A) The coprolite rendered semi-transparent with inclusions, such as beetle remains and fibrous networks, representing fungal colonies or algae visible. Top corner: silhouette of Silesaurus opolensis, the most probable coprolite producer. (B–D) The holotype specimen of Triamyxa coprolithica in ventral (B), lateral (C), and dorsal (D) views. (E and F) The second complete specimen in ventral (E) and anterior (F) views. Individual ventrites are indicated by roman numerals. (G) Triamyxa coprolithica preserved in various degrees of disarticulation. (H) An isolated head and two elytra that do not belong to Triamyxa coprolithica but to slightly larger beetles that were also ingested by the coprolite producer. (I) Examples of individual remains of Triamyxa coprolithica (meso- and metaventrite, head, head attached to pronotum, and three pronota). (J) Two of numerous elytra of similar size and morphology attributed to T. coprolithica. (K) Fibrous structures interpreted as fungi or algae. (L) A possible decomposed wood fragment. Color coding: blue,eyes; purple, antennae;light purple,legs. Abbreviations:abd,abdomen;ant,antenna; cox, coxa;ey, eye; fem, femur; hd, head;lgs, legs;pp, propleuron; thx, thorax; tib, tibia; troch, trochanter; trs, tarsi; ventr, ventrites. See also Figure S1.