Arethaea solterae Heads, Thomas & Hedlund, 2023

HEADS, SAM W., THOMAS, M. JARED, HEDLUND, TYLER J. & WANG, YINAN, 2023, A new fossil katydid of the genus Arethaea Stål (Orthoptera: Tettigoniidae) with exceptionally preserved internal organs from the Eocene Green River Formation of Colorado, Palaeoentomology 6 (3), pp. 268-277 : 270-273

Arethaea solterae Heads, Thomas & Hedlund sp. nov.

urn:lsid:zoobank.org:act:38B8E841-8A01-4CEC-8FA4-6D328C81AE9F

( Figs 2 , 3 )

Holotype. INHS-P 2190-1: Adult male preserved in right lateral aspect on a roughly square slab of shale measuring 95×98× 6 mm. Several other insects are present on the slab including: fragmentary hymenopteran wings [ INHSP 2190-2], a ground beetle ( Coleoptera : Carabidae ) [ INHSP 2190-3], two froghoppers ( Hemiptera : Cercopoidea) [ INHS-P 2190-6 and INHS-P 2190-7], and two very fragmentary indeterminate insects [ INHS-P 2190-4 and INHS-P 2190-5].

Etymology. The specific epithet honours our dear friend and colleague Dr Leellen Solter, whose hard work and dedication, both in the field and lab, have vastly improved the INHS Fossil Insect Collection.

Diagnosis. The new species is separated from congeners by the following combination of characters: [1] pronotal disc almost completely flat with no apparent elevation or elaboration of the metazona; [2] principal sulcus of pronotum weakly developed; [3] metafemur

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approx. seven times longer than pronotum and approx. 70% as long as metatibiae; [4] first abdominal tergite without prominent glandular process.

Type locality and horizon. USA: Colorado: Rio Blanco County: approximately 35 km south of Meeker on County Road 5: 39.7291, -107.9768. Green River Formation : Parachute Creek Member (Eocene:Ypresian— Lutetian) .

Description. Body form cryptic, typical of the genus. Head elongate, with fastigium verticis and frons produced somewhat anteriorly; antennae incomplete, very long and slender; eye faintly preserved but apparently elongate and elliptic in form; mouthparts well-sclerotised, elongate. Thorax with “hump-like” form typical of the genus; pronotum sellate, disc almost completely flat, metazona not elevated, lateral margin broadly rounded with distinct marginal carina; meso- and metathoraces with welldeveloped flight muscles visible. Tegmina long, narrow, missing apices, at least twice as long as abdomen, venation indistinctly preserved. Legs extremely long and slender, typical of the genus; proleg incompletely preserved, with profemur at least one-third longer than pronotum, and protibia bearing tiny spines; mesoleg not preserved; metafemur extremely slender, approx. seven times as long as pronotum; metatibia extremely slender, approx. threetenths longer than metafemur, bearing two rows of small, well-sclerotised dorsal spines along entire length; 1 st and 2 nd metatarsomeres of equal length; 3 rd metatarsomere slightly shorter, with pad projecting somewhat distally; 4th metarsomere at least twice as long as 3 rd, gently curved, with prominent tarsal claws. Abdomen approx. half as long as tegmina; 1 st tergite simple, lacking prominent tooth-like glandular process; entire abdomen preserved in sagittal section with internal soft tissues exceptionally preserved; anterior midgut (ventriculus) coiled, preserved as dark organic compression; at least five distinct tubulelike structures present in posterior half of abdominal cavity associated with a small but distinct ovoid structure closely resemble accessory glands and testis, with other undifferentiated soft tissues resembling fat body.

Measurements. Total body length approx. 18.0 mm; head 2.9 mm long (measured from vertex to apex of mouthparts); pronotum 2.5 mm long; tegmina at least 21.6 mm (apical part not preserved); profemur at least 7.4 mm long (not completely preserved); metafemur approx. 19.0 mm long; metatibia 27.1 mm; metabasitarsus approx. 0.6 mm long; 2nd metatarsomere approx. 0.6 mm long; 3rd metatarsomere approx. 0.4 mm; 4th metatarsomere approx. 0.8 mm long; abdomen 11.4 mm long.

Remarks. The assignment of A. solterae sp. nov. to Arethaea is strongly supported by its extremely long and slender legs (profemur approximately 2.5× the length of the pronotum and metafemur at least twice as long as the abdomen), very narrow tegmina (in males at least more than 8× longer than wide), and eyes markedly elongate and elliptic (see Hebard, 1936; Capinera et al., 2004). Detailed comparison of A. solterae sp. nov. with extant species of the genus is limited by the preservation of the specimen. While exceptionally well-preserved, the holotype of A. solterae sp. nov. being preserved as an organic compression in right lateral aspect ( Fig. 2A ) makes assessment of the posterior margin of the pronotum (a character used to separate extant species) impossible. Moreover, the cerci, which are also an important character used to delimit extant species, are not preserved in A. solterae sp. nov. The form of the apices of the pro- and mesofemora was noted as being particularly useful in separating species by Hebard (1936), though are also insufficiently preserved in A. solterae sp. nov. to be informative. Nevertheless, it is clear that the first abdominal tergite in A. solterae sp. nov. does not bear the prominent, somewhat tooth-like glandular process typical of many species of the genus. In this respect, A. solterae sp. nov. most closely resembles A. sellata , with which it also shares similar relative proportions (see Rehn, 1907), but differs in being slightly larger and with the dorsal surface of the pronotum being generally flat, without any notable elevation of the metazona. While the latter character state may be plesiomorphic, it is a feature known only in A. solterae sp. nov., readily separating it from all extant species of the genus.

Figures

FIGURE 2. Arethaea solterae sp. nov. (holotype male INHS-P2190-1). A, Habitus, right lateral view. B, Close-up view of head and pronotum.

FIGURE 3. Arethaea solterae sp. nov. (holotype male INHS-P2190-1). A, Wings. B, Thorax and abdomen with interpretation of internal structures. C, Metatibiae and metatarsi.Abbreviations: ag, accessory glands; fb, fat body; tes, testis; txm, thoracic muscles; vt, ventriculus (anterior midgut).