Gigamachilis

Gigamachilis Temporal range: Late Ladinian, 239.5–237.0  Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type specimen
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Archaeognatha
Family:	Machilidae
Genus:	† Gigamachilis Montagna, Haug, Strada, Haug, Felber & Tintori, 2017
Species:	†G. triassicus
Binomial name
†Gigamachilis triassicus Montagna, Haug, Strada, Haug, Felber & Tintori, 2017

Gigamachilis is an extinct genus of jumping bristletails in the family Machilidae. The genus consists of a single species, Gigamachilis triassicus. ^{[1] [2]} The species is the largest archaeognath that ever existed. ^{[3] [4] [5]}

The species was described by Matteo Montagna, Joachim T Haug, Laura Strada, Carolin Haug, Markus Felber and Andrea Tintori. ^{[3] [5]}

Gigamachilis triassicus has an estimated total length of approximately 80 millimetres, representing the largest apterygote insect ever recorded. ^{[3] [5]}

The fossil was found in the Meride Formation of Monte San Giorgio, Switzerland in Middle Triassic (Ladinian)-aged strata. ^[6] The holotype preserved four abdominal ganglia, optic lobes with neuropils and compound retina and muscular bundles. ^{[3] [5]}

Etymology

The prefix 'Giga-', derived from the Greek word gígas means giant, indicating to the very large size of the insect. The suffix '-machilis' is derived from the family name Machilidae to which Gigamachilis is ascribed. The word Latin word triassicus refers to the Triassic Period. ^[3]

Distribution

The specimens of Gigamachilis were found only in the Meride Formation of Monte San Giorgio, Switzerland. ^{[3] [5]}

Phylogeny

Schematic reconstructions of Gigamachilis and Dasyleptus , with alternative scenarios of Archaeognatha evolution.

The phylogenetic placement of Gigamachilis has been clarified through recent total-evidence analyses of Archaeognatha that incorporate both morphological and fossil data. Gigamachilis triassicus was included in reanalyses of the phylogenetic framework proposed by Zhang et al. (2018), ^[7] alongside additional extinct and extant taxa. ^[4]

These analyses consistently recovered Gigamachilis triassicus within the family Machilidae, confirming its attribution to the crown group of jumping bristletails. This placement demonstrates that Machilidae were already present during the Middle Triassic, extending the minimum known age of the family by approximately 100 million years compared with previous estimates. ^[4]

The confirmed machilid affinities of Gigamachilis highlight its importance for understanding the early evolutionary history and temporal diversification of Archaeognatha. ^[4]

Morphology

General

Gigamachilis triassicus has large maxillary palps with several elements. The species has abdominal coxopodites with coxopodal vesicles and styli, paired annulated cerci and filum terminale with basal parts preserved. This characteristics place the species in the order Archaeognatha. ^{[3] [5]}

The presence of styli-like structures on the second thoracic leg and of scales on appendages places the species in the family Machilidae. ^{[3] [5]}

The specimen with head and thorax slightly rotated in the sagittal plane, only visible in ventral view. Body length from the apex of the head to the apex of the last abdominal segment, excluding filum terminale, is 40 mm (1.6 in). Maximum body width is 12.5 mm (0.49 in) (second thoracic segment). On the base of the ratio between the length of the filum terminale and that of the whole organism in extant taxa, the length of G. triassicus was estimated in approximately 80 mm (3.1 in). ^{[3] [5]}

Head

Gigamachilis triassicus has very large eyes which are developed laterally. Antennae were found partially preserved with only proximal parts visible which included antennal socket, scapus, pedicellus and a portion of the annulated flagella (length 2.9 mm (0.11 in)). Mouthparts were found partially preserved. The terminal element of the right labial palp and the first three elements of the large leg-like maxillary palps are visible. Labium prementum, maxillary palpifers and glossae are partially visible. ^{[3] [5]}

Thorax

Total length of the thorax of G. triassicus is 9.8 mm (0.39 in) and the maximum width at mesothorax is 12.5 mm (0.49 in). Impression of lateral rims of pronotum and mesonotum preserved are on the right side (respectively 1.8 mm (0.071 in) and of 3.6 mm (0.14 in) long, mesonotum thickness is 0.6 mm (0.024 in)) The rim of mesonotum partially preserved on the left side. Procoxae (length: right 3.9 mm (0.15 in), left 3.3 mm (0.13 in)), proximal part of protrochanters, mesocoxae (length: right 4.2 mm (0.17 in), left 2.8 mm (0.11 in)) and mesotrochanters (length: right 3.5 mm (0.14 in), left 4.3 mm (0.17 in)) preserved. Left mesocoxa bearing the proximal part of the coxal stylet (length 0.9 mm (0.035 in)). Trochanter is distally lobe-shaped. Right metacoxa (length 4.7 mm) and metatrochanter are preserved (length 9.2 mm (0.36 in)). The first bearing coxal stylet (length 4.3 mm (0.17 in)), setae (length 0.35 mm (0.014 in)) and scales are visible. Left metatrochanter are only partially visible. ^{[3] [5]}

Abdomen

The abdomen of G. triassicus is composed of 10 visible segments, the first only partially visible on the right side, the last segment bearing the proximal part of the two cerci and of the filum terminale. The total length is 26.3 mm (1.04 in). The maximum width at abdominal metamere I 10.1 mm (0.40 in). Inferior rim of the tergite and right coxopodite preserved on abdominal metameres I to VIII, whereas in metamere IX, these structures are visible but poorly preserved. Coxopodal vesicles are present on abdominal segments I to VII. Abdominal styli are clearly visible on abdominal appendages II (left) and IV (right). Cerci and filum terminale on segment X are partially preserved. ^{[3] [5]}

References

1. "Gigamachilis triassicus Montagna, Haug, Strada, Haug, Felber & Tintori, 2017". www.gbif.org. Retrieved 2026-02-11.
2. "MorphoBank V4". www.morphobank.org. Retrieved 2026-02-17.
3. Montagna, Matteo; Haug, Joachim T.; Strada, Laura; Haug, Carolin; Felber, Markus; Tintori, Andrea (2017-04-07). "Central nervous system and muscular bundles preserved in a 240 million year old giant bristletail (Archaeognatha: Machilidae)". Scientific Reports. 7 (1) 46016. doi: 10.1038/srep46016 . ISSN   2045-2322. PMC   5384076 . PMID   28387236.  This article incorporates textfrom this source, which is available under the CC BY 4.0 license.
4. Montagna, Matteo (April 2020). "Comment on Phylogenetic analyses with four new Cretaceous bristletails reveal inter‐relationships of Archaeognatha and Gondwana origin of Meinertellidae". Cladistics. 36 (2): 227–231. doi: 10.1111/cla.12387 . ISSN   0748-3007. PMID   34618953. S2CID   199633962.
5. "Gigamachilis". ResearchGate . Retrieved 17 February 2026.
6. "PBDB". paleobiodb.org. Archived from the original on 2022-03-09. Retrieved 2026-02-15.
7. Zhang, Weiting; Li, Hu; Shih, Chungkun; Zhang, Aibing; Ren, Dong (2017-07-11). "Phylogenetic analyses with four new Cretaceous bristletails reveal inter‐relationships of Archaeognatha and Gondwana origin of Meinertellidae". Cladistics. 34 (4): 384–406. doi:10.1111/cla.12212. ISSN   0748-3007. Archived from the original on 2022-09-21.