The oldest Bibio Geoffroy, 1762 (Diptera: Bibionidae) from the Paleocene of Menat (France)

Abstract

The lacustrine Konservat-Lagerstätte of Menat (Puy-de-Dôme, France) is a unique window in the terrestrial Paleocene environments of Western Europe (Wedmann et al., 2018). It has yielded an exceptional diversity of plants (leaves, flowers, seeds, pollen), and animals (vertebrates and arthropods, especially insects) (e.g., Piton, 1940). Nevertheless, flies are quite rare in this outcrop in which the paleo-entomofauna is dominated by beetles (69% of a collection of 3938 specimens). To date, this paleo-maar has given only one specimen of the family Bibionidae, a Plecia sp. (Nel, 2007). Piton (1940) also described a ‘Bibio sp.’, but Nel (2007) reexamined the two specimens of Piton, concluding that they are not bibionids. Thus, this family is clearly very rare in this outcrop. The Bibionidae seem to be quite rare in the Paleocene and early to middle Eocene outcrops of Western Europe (Oise amber, Baltic amber, Messel) (Gee et al., 2001; Nel, 2007; Skartveit & Wedmann, 2015; Skartveit, 2021). They are also rather rare in the late Eocene of the Isle of Wight (Krzemiński et al., 2019), while they are much more frequent in the younger, late Eocene, Oligocene, or Miocene paleolakes of France, Germany, and Spain (e.g., Monteils, Rott, Cereste, Dauphin, Aix-en-Provence, Rubielos de Mora, Ribesalbes, Montagne d’Andance, Sainte-Reine) (Peñalver-Molla, 1998, 2002; Skartveit & Nel, 2017; Skartveit & Wedmann, 2021). They are the most frequent insects in these outcrops.

Full text

226 Submitted: 24 Apr. 2023; accepted by D. Azar: 29 May 2023; published: 13 Jun. 2023
Palaeoentomology 006 (3): 226–229
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Copyright © 2023 Magnolia Press
PALAEOENTOMOLOGY
ISSN 2624-2826 (print edition)
ISSN 2624-2834 (online edition) PE
Short
Communication
The lacustrine Konservat-Lagerstätte of Menat (Puy-
de-Dôme, France) is a unique window in the terrestrial
Paleocene environments of Western Europe (Wedmann et
al., 2018). It has yielded an exceptional diversity of plants
(leaves, flowers, seeds, pollen), and animals (vertebrates
and arthropods, especially insects) (e.g., Piton, 1940).
Nevertheless, flies are quite rare in this outcrop in which
the paleo-entomofauna is dominated by beetles (69% of a
collection of 3938 specimens). To date, this paleo-maar
has given only one specimen of the family Bibionidae,
a Plecia sp. (Nel, 2007). Piton (1940) also described a
‘Bibio sp.’, but Nel (2007) reexamined the two specimens
of Piton, concluding that they are not bibionids. Thus, this
family is clearly very rare in this outcrop. The Bibionidae
seem to be quite rare in the Paleocene and early to middle
Eocene outcrops of Western Europe (Oise amber, Baltic
amber, Messel) (Gee et al., 2001; Nel, 2007; Skartveit &
Wedmann, 2015; Skartveit, 2021). They are also rather rare
in the late Eocene of the Isle of Wight (Krzemiński et al.,
2019), while they are much more frequent in the younger,
late Eocene, Oligocene, or Miocene paleolakes of France,
Germany, and Spain (e.g., Monteils, Rott, Cereste, Dauphin,
Aix-en-Provence, Rubielos de Mora, Ribesalbes, Montagne
d’Andance, Sainte-Reine) (Peñalver-Molla, 1998, 2002;
Skartveit & Nel, 2017; Skartveit & Wedmann, 2021). They
are the most frequent insects in these outcrops.
Here we describe the first fly from Menat attributable
to the subfamily Bibioninae. Thus only two bibionids have
been found there, in a collection of ca. 4000 fossil insects.
By comparison, the Bibionidae represent 25% of the fossil
insects collected at Cereste, in a collection of ca. 8,000
insects (Nel, 1991).
Material and methods
The middle Paleocene Menat fossil site, small outcrop near
the southeast of the village of Menat (46°06′ N, 2°54′ E,
Menat Basin, Puy-de-Dôme, France), is a volcanic maar
containing a rather small paleolake ca. 1 km in diameter, filled
with sedimentary rocks (spongo-diatomites) with remains of
diverse aquatic and terrestrial flora and fauna (Piton, 1940;
Nel, 1989, 2008, 2022; Nel & Roy, 1996; Garrouste et al.,
2017; Legalov et al., 2019; Jouault & Nel, 2022; Nel &
Jouault, 2022). The composition of faunal and floral remains
suggests that this lake was surrounded by a forest and that
the paleoenvironment was warm and humid (Wedmann et
al., 2018). The age of the Menat outcrop was estimated as
ca. 59 Ma, based on pollen, mammalian stratigraphic, and
radiometric K/Ar analyses (Kedves & Russell, 1982; Nel,
2008). However, a new estimate based on macroflora study
postulated its age within 61–60 Ma (Wappler et al., 2009).
The fossil was collected in 2021 in a small outcrop situated
close to the ‘Etablissement d’Hébergement pour Personnes
Agées Dépendantes’ (EHPAD) of Menat.
The fossil was studied using a stereomicroscope
Olympus SCX9 in the Muséum national d’Histoire naturelle
of Paris (MNHN). Photographs were taken with a Nikon
SMZ 25 stereomicroscope with an attached Nikon D800
digital camera or using a Canon 50D with a 65 MPE camera
lens mounted on an automated stacking rail (StackShot).
All images are digitally stacked in a photomicrographic
composites deriving of several individual focal planes,
which were obtained using Helicon Focus. The figures
were composed with Adobe Illustrator CC2019 and Adobe
Photoshop CC2019 software.
Systematic palaeontology
Order Diptera Linnaeus, 1758
Family Bibionidae Newman, 1834
Subfamily Bibioninae Newman, 1834
Genus Bibio Geoffroy, 1762
https://doi.org/10.11646/palaeoentomology.6.3.3
http://zoobank.org/urn:lsid:zoobank.org:pub:B46EC950-8E26-4901-A076-3B380D0A778D
The oldest Bibio Geoffroy, 1762 (Diptera: Bibionidae) from the Paleocene of
Menat (France)
ANDRÉ NEL & JEAN-PAUL KUNDURA
Institut de Systématique, Évolution, Biodiversité (ISYEB) Muséum national d’Histoire naturelle, CNRS, Sorbonne Université, EPHE,
Université des Antilles, CP50, 57 rue Cuvier 75005 Paris, France
�
anel@mnhn.fr; https://orcid.org/0000-0002-4241-7651
�
kundura.jean-paul@neuf.fr; https://orcid.org/0009-0008-3914-3515

THE OLDEST BIBIO GEOFFROY, 1762 Palaeoentomology 006 (3) © 2023 Magnolia Press • 227
Bibio sp.
(Fig. 1)
Material. Specimen MNT Nel 1171 (part and counterpart of
an adult fly with apex of abdomen missing), deposited in the
“Musée de Paléontologie de Menat”¸ Menat, Puy-de-Dôme,
France.
Type locality and horizon. New quarry, Menat, Puy-
de-Dôme, France; middle Paleocene, Menat Basin.
Description. Total body length 8.2 mm. Head length
0.9 mm, width 1.1 mm. Palp small, brown. Antenna very
short, 0.7 mm long, brown, with eight (?) flagellomeres.
Ocellar tubercle not very prominent.
Thorax: mesonotum 2.4 mm long, black, with sparse
setation poorly preserved; haltere not preserved. Fore tibia
with a strong spur and a strong anterior projection, spur
almost as long as anterior projection. Protarsus slender. Mid
legs not preserved. Hind femur 2.4 mm long, 0.6 mm wide,
tibia 1.8 mm long, 0.2 mm wide, tarsus not preserved.
Wing ca. 4.9 mm long, 2.0 mm wide, light brown
infuscate, stigma dark brown; visible veins brown, bare,
R-veins thickened. C not extending beyond apex of Rs. Rs
nearly reaching wing apex, with its basal part 0.4 mm long;
R1 ending on C at 3.3 mm of wing base; Rs and M touching
in one point. Branches of M, cubital and anal veins extremely
faint, hardly visible.
FIGURE 1. Bibio sp., Menat. Specimen MNT Nel 1171. Photographs. A, Part. B, Counterpart. Scale bar = 4 mm.

NEL & KUNDURA
228 • Palaeoentomology 006 (3) © 2023 Magnolia Press
Abdomen brown, narrow, slightly elongate (possibly a
male), preserved part 3.9 mm long, 1.3 mm wide. Terminalia
not preserved.
Discussion
The presence of a strong elongate anterior projection
and spine on fore tibia and the venation with a simple Rs
indicate that this fossil belongs to the family Bibionidae, to
the subfamily Bibioninae, and to the group Bibio, Bibiodes
Coquillett, 1904 (incl. the fossil genus Bibiodites Cockerell
1915, after Skartveit, 2009), Bibionellus Edwards, 1935,
and Enicoscolus Hardy, 1961. Affinities with the Mesozoic
subfamily Cretobibioninae Skartveit & Ansorge, 2020 are
excluded because that subfamily a vein R2+3 and fore legs
without spine (Skartveit & Ansorge, 2020).
The radial sector just touching M rather than being fused
with M for some distance excludes affinities with the genus
Bibiodes (Skartveit & Wedmann, 2021). The C not extending
beyond apex of Rs excludes the affinities with the genus
Bibionellus (Pinto & de Souza Amorim, 1997). Enicoscolus
has the apex of vein Rs more basal than in the new fossil
and the basal section of Rs shorter or at most subequal to
r-m crossvein, which differs from the configuration found
in the new fossil (Hardy, 1961, 1962; Fitzgerald, 1997).
Interestingly, the branching patterns of M, the cubital and
anal veins extremely faint and hardly visible resemble the
configuration often recorded in Enicoscolus. However, we
consider that the faint preservation of the cubital and anal
veins rather results from the poor preservation of this area.
Otherwise, all the visible characters of the new fossil
fit with the current delineation of the genus Bibio, and we
consider it a representative of the latter genus. Unfortunately,
we cannot compare it with the other fossil and extant species
of Bibio because it lacks male genital appendages (a key
character discriminating Bibio species). We also refrain from
formally naming this fossil for this reason.
Conclusion
This fossil confirms the presence of the Bibionidae and
represents the first Bibioninae in the outcrop of Menat. It
is also the oldest record of the genus Bibio, as Skartveit
(2009: 4) attributed the Bibioninae from the early Upper
Cretaceous (93 Ma) of Botswana—described by Rayner
(1987)—to the genus Bibiodes (see also Skartveit, 2023:
fig. 5). Jarzembowski (1978) indicated the presence of a
Bibionidae in the upper Paleocene of the Isle of Mull in
Scotland (Lukashevich et al., 2021), which is younger than
the Menat outcrop.
It is extremely strange that this family remains so scarce
in the European Paleocene and Early to Middle Eocene, while
they are extremely frequent in the late Eocene, Oligocene,
or Miocene of Southern France, Spain, and Germany. This
situation is likely not a question of different ages because
they are also rather rare in the late Eocene of UK, while
they are quite frequent in the Eocene of British Columbia
(Canada) and the Green River (USA) (Wilson, 1978). The
factors causing these differences remain unknown. It is
possibly due to paleoclimatic differences or taphonomic
biases.
Acknowledgments
We sincerely thank Dr Enrique Peñalver (Instituto Geológico
y Minero de España, Museo Geominero) for his useful
remarks on the first version of the paper. We had the pleasure
to receive generous assistance from Bernard Duverger
(President of the Communauté de Communes of Menat
region), Clotilde Berger-Pompili and Mathilde Leygnac
(directors of the EHPAD du pays de Menat), for their kind
help and authorizations to collect fossil insects in a small
but rich outcrop near the village of Menat (Puy-de-Dôme,
France).
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