A new genus, Palaeatalasis gen. nov. (type species P. monrosi sp. nov.), from the tribe Megamerini
(Chrysomelidae: Sagrinae) from the early-middle Eocene Green River Formation
is described and illustrated. The new genus is similar to the Recent
Atalasis Lacordaire, 1845 but differs from it in the subparallel sides of the
pronotum, metafemora without teeth, and non-emarginate eyes. It differs from
the Eocene Eosagra Haupt, 1950 in the large, convex, non-emarginate eyes, wide
elytra, and transverse pronotum. The new genus is distinguished from the Paleocene Gallopsis Legalov, Kirejtshuk et Nel, 2019 in the wide forehead and convex
eyes. It is the first record of the Sagrinae from North America and the
fourth known species of the family Chrysomelidae from the Green River.
Introduction
Leaf beetles of the family Chrysomelidae, which are common inhabitants of
Recent ecosystems, develop on leaves or in different plant organs. Twelve
subfamilies, Sagrinae, Bruchinae, Donaciinae, Criocerinae, Cassidinae, Chrysomelinae, Galerucinae, Eumolpinae, Lamprosomatinae, Cryptocephalinae,
Spilopyrinae, and Synetinae, can be distinguished within the family (Bouchard et al., 2011; Reid, 2014). The earliest record of the subfamily
Chrysomelinae is in the Middle–Late Jurassic of Kazakhstan (Kirejtshuk et al., 2015), but these data require confirmation. The second fossil find of
this subfamily was from the middle Eocene of Germany (Haupt, 1956). The
first record of Bruchinae was from the mid-Cretaceous Burmese amber (Legalov
et al., 2020), Galerucinae from the Santonian Taimyr amber (Nadein and
Perkovsky, 2018), Donaciinae from the Danian of Russia (Bieńkowski,
2015) and the late Palaeocene of Canada (Askevold, 1990), Sagrinae and
Cryptocephalinae from the middle Paleocene of France (Piton, 1940; Legalov
et al., 2019), Eumolpinae from the early Eocene Oise amber (Moseyko et al.,
2010), Cassidinae from the early-middle Eocene of the USA (Chaboo and Engel, 2009), and Criocerinae from the late Eocene Baltic amber (Bukejs and
Schmitt, 2016). The Lamprosomatinae were described from Baltic amber (Bukejs
and Nadein, 2015; Bukejs, 2019). The Spilopyrinae and Synetinae are absent
from the fossil history. The fauna of Chrysomelidae from the Green River Formation (late-middle Eocene, USA) is poorly studied. Only three species, Eosacantha delocranioides Chaboo et Engel, 2009, Denaeaspis chelonopsis Chaboo et Engel, 2009 of the Cassidinae, and Cryptocephalus vetustus Scudder, 1878 of the Cryptocephalinae, were described. Lema pervetusta Cockerell, 1921,
which was listed from the Green River deposits (Santiago-Blay, 1994), belongs to the family Cerambycidae (Bukejs and Schmitt, 2016). The species described
in this study is the first find of the subfamily Sagrinae and the fourth
species of the family Chrysomelidae from the Green River Formation.
Material and methods
The holotype is deposited in the Institute of Systematics and Ecology of
Animals of the Siberian Branch of the Russian Academy of Science (Russia:
Novosibirsk) – ISEA.
Descriptions, photographs, and body measuring were performed using a Zeiss Stemi 2000-C dissecting stereomicroscope.
Terminology of body structures is based on Lawrence et al. (2010).
This article is registered in ZooBank (http://www.zoobank.org, last access:
16 April 2021) under LSID
LSIDurn:lsid:zoobank.org:pub:A2F174B6-F4C7-45E7-9CAD-EA6EF89051A6.
The name is formed from the Greek “palaios” (ancient) and the generic name “Atalasis”. Gender masculine.
Diagnosis
Large distinctly sclerotized beetle; head prognathous, without middle
sulcus, not constricted behind eyes; mandibles large; maxillary palpi long;
eyes suboval, convex, non-emarginate; forehead wider than width of rostrum
base; temples long; antennae filiform, reaching anterior third of elytra;
pronotum transverse; sides subparallel; elytra suboval, striate; sutural
stria deep, deeper than other striae; profemora and mesofemora moderately thickened; metafemora not toothed, distinctly larger than other femora;
abdominal ventrite 1 long, 2.5 times as long as ventrite 2.
Comparison
The new fossil genus is similar to the Recent Atalasis Lacordaire, 1845 but differs from it in the subparallel sides of the pronotum, non-emarginate eyes, and metafemora lacking teeth, whereas Atalasis is characterized by the pronotal sides
tapering from the apical part to the basal third, emarginate eyes, and metafemora with teeth. It differs from the Eocene Eosagra Haupt, 1950 in the large,
convex, non-emarginate eyes, wide elytra, and transverse pronotum. The new genus is distinguished from the Paleocene Gallopsis Legalov, Kirejtshuk et Nel, 2019 by the wide forehead and convex eyes.
Remarks
The head not narrowed basally, without rostrum, filiform antenna, and
striate elytra suggest placement of Palaeatalasis gen. nov. in the family Chrysomelidae.
The new genus belongs to the family Sagrinae based on the deep sutural
stria, deeper than other striae, the metafemora distinctly larger than other
femora, and the prognathous head without a median sulcus. The convex and
non-emarginate eyes suggest placement in the tribe Megamerini.
Body of the counterpart of Palaeatalasis monrosi sp. nov., holotype, GR2020/2 (ISEA). Scale bars = 1.0 mm.
Body outline of the counterpart of Palaeatalasis monrosi sp. nov., holotype, GR2020/2 (ISEA). Scale bars = 1.0 mm.
Etymology
Patronymic. This new species is named in memory of Francisco Monrós, who
studied Chrysomelidae.
Type material
Holotype. Holotype, ISEA, no. GR2020/2, counterpart of beetle.
Type stratum
Early-middle Eocene, Bridgerian, 53.5–48.5 Ma.
Type locality
United States: Utah, Uintah County, 3–4 km west of the railway crossing of the Green River, Green River Formation.
Description
Measurements. Body length (without rostrum) 17.7 mm, body maximum width 7.8 mm; pronotum
length 3.5 mm, pronotum maximum width 3.6 mm; length of antenna 9.2 mm.
Body. Brown, distinctly sclerotized.
Head. Prognathous, without middle sulcus and without rostrum. Head capsule not
constricted behind eyes. Labrum free. Mandibles large, curved. Maxillary
palpi long. Eyes large, suboval, strongly convex, non-emarginate. Forehead
wide, distinctly wider than width of rostrum base. Temples long, 0.6 times
as long as eye length.
Antennae. Antennae inserted before eyes, filiform, long, reaching anterior third of
elytra. Antennomere 1 oval, 1.3 times as long as wide. Antennomeres 2–10
conical. Antennomere 2 1.3 times as long as wide, 0.5 times as long as and
0.4 times as narrow as antennomere 1. Antennomere 3 1.7 times as long as
wide, 1.3 times as long as and equal in width to antennomere 2. Antennomere 4 2.0 times as long as wide, 1.3 times as long and 1.1 times as wide as antennomere 3. Antennomeres 5–9 subequal in width. Antennomere 5 2.4 times
as long as wide, 1.4 times as long as antennomere 4. Antennomere 6 1.8 times
as long as wide, 0.7 times as long as antennomere 4. Antennomeres 7–10
subequal in length. Antennomere 7 2.2 times as long as wide, 1.3 times as
long as antennomere 6. Antennomere 10 2.8 times as long as wide, 1.1 times
as long as and 0.9 times as narrow as antennomere 9. Antennomere 11 3.0 times as long as wide, 1.1 times as long as and equal in width to
antennomere 10, weakly pointed at apex.
Pronotum. Weakly transverse, with subparallel sides, 0.9 times as long as wide in
middle. Base 0.6 times as narrow as elytral base.
Elytra. Suboval, with weak humeri, weakly striate, 1.9 times as long as wide at
base, 1.6 times as long as wide in middle, 2.3 times as long as wide at
apical fourth, 3.6 times as long as pronotum. Interstriae quite wide.
Punctate striae weak, with small rounded and dense punctures.
Thorax. Metacoxal cavities transverse.
Legs. Profemora and mesofemora moderately thickened. Metafemora enlarged without tooth, distinctly larger than other femora. Tibiae slightly curved, with
carina. Mesotarsomere 1 conical. Mesotarsomere 3 bilobed.
Abdomen. Abdominal ventrite 1 long, 1.5 times as long as metacoxal cavity length.
Ventrite 2 0.4 times as long as ventrite 1. Ventrite 3 0.8 times as long as
ventrite 2. Ventrite 4 1.23 times as long as ventrite 3. Ventrite 5 slightly
longer than ventrite 4.
Discussion
Members of the Sagrinae were found in the middle Paleocene of France
(Legalov et al., 2019) and the Eocene of Germany (Wappler, 2003; Wedmann,
2018). Formerly they were not known from the rich Lagerstättten of the United States, such as the Green River and Florissant, nor from Eocene Baltic amber (Kirejtshuk and Ponomarenko, 2018). This study is the first record of
Sagrinae from North America. The Paleocene and Eocene Sagrinae belong to the
tribe Megamerini, which is now distributed in Australia and southern South
America and Madagascar (Monrós, 1960). This subfamily is now absent from
the central and northern parts of South America, central and North America, the West Indies, the African deserts, and also the Palaearctic. In the
Western Hemisphere, the Sagrinae are distributed (Fig. 3) in tropical Africa, Madagascar, South and Southeast Asia, the Sunda Islands, and New Guinea, but the
centre of their diversity is located in Australia. It can be assumed that Megamerini were previously distributed on all continents and were the most ancient and primitive Sagrinae. Primitive characteristics of the Megamerini are the striate elytra, convex, non-emarginate eyes, and head without rostrum.
Distribution of Sagrinae: Recent members – green shaded area, octagram – fossil record from the Green River, star – record from Menat, circle – German Eocene record.
Sample availability
The specimen is deposited in the Institute of Systematics and Ecology of
Animals, Siberian Branch, Russian Academy of Sciences.
Competing interests
The author declares that there is no conflict of interest.
Acknowledgements
The author thanks Boris A. Korotyaev and Alexey G. Moseyko
(St. Petersburg) for the opportunity to study comparative material of the subfamily Sagrinae from the Zoological Institute RAS, George O. Poinar, Jr. (USA: Corvallis) for improving the manuscript, and two reviewers for valuable suggestions.
Review statement
This paper was edited by Florian Witzmann and reviewed by two anonymous referees.
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