Kimmeridgebrachypteraeschnidium

Kimmeridgebrachypteraeschnidium Temporal range: Late Jurassic PreЄ Є O S D C P T J K Pg N ↓
Holotype wing of Kimmeridgebrachypteraeschnidium.
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Hexapoda
Clade:	Crustacea
Class:	Insecta
Subclass:	Pterygota
Infraclass:	Palaeoptera
Order:	Odonata
Infraorder:	Anisoptera
Family:	†Aeschnidiidae
Genus:	†Kimmeridgebrachypteraeschnidium
Species:	†K. etchesi
Binomial name
†Kimmeridgebrachypteraeschnidium etchesi Fleck & Nel, 2003

Kimmeridgebrachypteraeschnidium (/ˌkɪməˌrɪdʒˌbrakˌitɛreɪstʃnˈɪdˌiʌm/) (meaning "Kimmeridge arm winged small darner" in Ancient Greek) is an extinct genus of large dragonfly (Anisoptera) from the Late Jurassic epoch (Kimmeridgian stage) of England. It possesses one of the longest genus names of any known species, with 31 letters.
Only one species in this genus is described, K. etchesi. It belonged the the extinct family of small darners, Aeshnidiidae.

History of research

Discovery

Vicinity of K. etchesi holotype based on referenced coordinates in Fleck & Nel 2003

Hurricane-force winds ripped pieces of red sediment from the cliffs at Kimmeridge Bay in southern England in 1987 or 1989. After the storm, paleontologist Steve Etches traversed the beaches of the bay with a hammer to split open rocks. He found a preserved dragonfly wing, and later on, the first known comfirmed ammonite eggs. The location was near the coordinates 50. 619999, -2.117. Elevation at this spot is about 98.4 meters (according to Avenza Maps). The dragonfly specimen is now displayed at the Etches Collection Museum, under the catalogue identification MJML K619. The counterslab is also in the collection as "K619b".

Further study

MJML K619 is the only known terrestrial insect preserved in the Kimmeridge Clay Formation. The specimen, which was a right forewing, was included in a study of the extinct Aeschnidiidae family by paleontologists Gunther Fleck and Andre Nel in 2003. In the paper, they formally described the Kimmeridge wing, establishing it as a holotype specimen and giving it the name Kimmeridgebrachypteraeschnidium etchesi. The specific name honors its collector.

Paleobiology

Description

Size graph based on K. etchesi wing by Ta-tea-two-te-to

The holotype forewing of K. etchesi measures roughly 7.5 cm (2.95 in) in length. A 2013 study reported a mean forewing length of 29.38 mm for over 70 extant dragonfly species. Thus, K. etchesi was large not only in regards to its genus name. No other parts of the animal's body have been uncovered, making an accurate reconstruction of its proportions difficult to estimate.

Affinities

Aeshna subarctica, or subarctic darner, a close living relative of the aeschnidiids

Kimmeridgebrachypteraeschnidium belonged to the extinct family of dragonlies called Aeschnidiidae, also called the small darners. The small darners thrived during the late Mesozoic Era before being driven to extinction by the impact of the Cretaceous/Paleogene extinction event. Being from the Kimmeridgian stage (157.3 to 152.1 MBC), K. etchesi is the oldest recorded member of the family. Later taxa are known from Konservat-Lagerstätte formations such as the Solnhofen limestone in Germany and the Yixian in China. Species have also been found in Oceania, South America, and Africa, and North America.

Aeshnidae is an extant dragonfly family including the true darners. The name 'Aeshnidiidae' was derived from the former.

Paleoecology

Abiotic

Location of the Kimmeridge Clay Formation during the Late Jurassic (green) and Holocene (brown), indicating continental shift over time. Captured with PALEOMAP

The Kimmeridge Clay Formation was deposited during the Jurassic period, specifically the Kimmeridgian stage, 157 to 152 MBC. It lies over Anglia and Dorset and is present in much of the North Sea. Generally, mudstones dominate the formations, with siltstone and sandstones being less common. The strata measure roughly 500 m (1640 ft) in thickness onshore, with lower measurements in the southern and higher in the northern North Sea. When the formation was being deposited, Europe was a cluster of islands in the Tethys Ocean. A marine, coastal environment is preserved.

Biotic

Kimmeridge Clay Formation mudstone, photographed Tony Jolliffe

The Jurassic Tethys Ocean was populated by a variety of organisms including marine reptiles, ammonites and other cephalopods, fishes, cartilagenous fishes, and bryozoans. On the coast, dinosaurs and insects like Kimmeridgebrachypteraeschnidium were present. Among the highlights of the Kimmeridge ecosystem is a giant Pliosaurus sp known from the most complete pliosaur skull ever found. Nicknamed the "Sea Rex", it was the subject of a 2024 documentary, David Attenborough and the Giant Sea Monster.

Steve Etches points at the holotype of K. etchesi, at the Etches Collection Museum

Pterosaurs flew above the waves here. Among them is a species of Rhamphorhynchus, R. etchesi, exclusive to the formation. It and several other taxa (including K. etchesi) are named after Steve Etches, who established the Etches Collection Museum in Kimmeridge and discovered thousands of fossils in the vicinity. Metriorhynchids like Geosaurus, ichthyosaurs such as Ophthalmosaurus and plesiosaurs like Colymbosaurus were included in the marine reptile diversity here. Sauropods and ornithopods (including Cumnoria) are the primary dinosaurs that lived on the Tethys islands here. A basal tyrannosauroid, Juratyrant, is also found here.