ELECTROHEMIPHLEBIA BARUCHELI
GEN.
ET SP. NOV. ( FIGS 1–14
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, 20A, B
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)
Etymology: The specific epithet is a patronymic one, proposed by Paul Tafforeau, honouring José Baruchel, head of the imaging group of the ESRF, as without him, palaeontology would never had developed so importantly at the ESRF.
Material:
Holotype specimen
ARC 372.1
View Materials
, a complete thorax attached to head and to the basal parts of the four wings, deposited in the Department Histoire de la Terre, Muséum National d’Histoire Naturelle, Paris. All the tomographic data as well as a surface model of the specimen are available upon request from the first author, and will be deposited in the public palaeontological database project of the ESRF when available. Reference 3D prints of the extracted specimens are deposited in the Muséum National d’Histoire Naturelle (
Paris
, France), in the Géosciences laboratory (Rennes, France), and at the ESRF (Grenoble, France).
Type locality:
Archingeay-Les Nouillers
; Charente-
Maritime
; south-west France; Mid Cretaceous; Uppermost Albian (lithological subunit A1 sensu Néraudeau, Thierry & Moreau, 1997)
.
Diagnosis: As for the genus (vide supra). Description: Forewing: petiole short, with AA separating from AP near wing base; one row of two long cells between AA and AP, between wing base and point of fusion between AA and CuA; CuP weakly curved, just distal cross-vein between two cells of anal area, between Ax1 and Ax2, but nearer level of Ax1 than that of Ax2, 0.2 mm distal of level of Ax1; no secondary antenodal cross-vein; arculus 0.2 mm distal of Ax2; distance between wing base and Ax1 1.2 mm, between Ax1 and Ax2 0.8 mm; distance between wing base and nodus about 4.5 mm, between arculus and nodus 2.5 mm; median and submedian spaces free; discoidal cell basally opened; RP + MA, basal part of MA and MAb aligned or nearly so; angle between MAb and MP + CuA rather acute in discoidal cell; MAb 0.5 mm long; basal part of MA 0.3 mm long; MP with a strong curve near its base; terminal kink of CP at nodus reduced; nodal Cr of normal obliquity; subnodus vertical; MP reaching posterior wing margin about two to three cells distal base of RP2; basal part of postdiscoidal area poorly preserved but probably one row of cells between MA and MP; base of RP3/4 between arculus and nodus, very close to nodus; base of IR2 opposite subnodus; one cell between base of RP3/4 and IR2; base of RP2 two cells distal of subnodus; subnodus apparently with a normal obliquity, not vertical; only two basal postnodal cross-veins and two basal postsubnodal cross-veins preserved, not aligned; no oblique cross-vein between IR2 and RP2.
Hindwing: petiole short, with AA separating from AP near wing base; one row of two long cells between AA and AP, between wing base and point of fusion between AA and CuA; CuP weakly curved, just distal cross-vein between the two cells of anal area, between Ax1 and Ax2, but nearer the level of Ax1 than that of Ax2, 0.3 mm distal of level of Ax1; distance between wing base and Ax1 1.5 mm, between Ax1 and Ax2 0.9 mm; no secondary antenodal cross-vein; arculus 0.2 mm distal of Ax2; median and submedian spaces free; discoidal cell basally closed, with a distinct angle in MA at its point of contact with basal side of discoidal cell, and an angle between MA and MAb; basal part of MA (anterior side of discoidal cell) 0.5 mm long, MAb 0.8 mm long, posterior side 1.1 mm long, basal side 0.3 mm long; terminal kink of CP at nodus reduced; nodal Cr of normal obliquity; subnodus vertical; MP with a strong curve near its base; one row of cells between MA and MP and between MP and CuA; CuA strongly zigzagged in its distal part, with one to two rows of cells between it and posterior wing margin; base of RP3/4 between arculus and nodus, close to nodus; base of IR2 opposite nodal Cr and subnodus, 0.5 mm distal of base of RP3/4; area between RA and RP broadened at level of base of RP3/4; one cell between bases of RP3/4 and IR2; subnodus not visible; base of RP2 two cells distal of subnodus; no oblique cross-vein between IR2 and RP2; areas between RP3/4 and MA and between RP3/4 and IR2 both with one row of cells, distally broadening, but with distal part missing; pterostigma and pterostigmal brace not preserved.
Body: Head 3.68 mm wide; compound eye broad, 1.02 mm wide in frontal view; distance between eyes 1.65 mm, head not very transverse; antennal scape very strong, distinctly longer than wide, about twice as long as wide; pedicel well developed; flagellum reduced to a tiny bristle, 0.6 mm long; labrum weakly developed, gibbose, transverse, 0.3 mm long, 0.8 mm wide, with lateral margin rounded, mandibles well exposed; anteclypeus clearly visible, small, 0.1 mm long, 0.2 mm wide, postclypeus broader than labrum, 0.3 mm long, 1.0 mm wide; clypeo-frontal sulcus deeply impressed; anterior part of frons with two strong gibbosities separated by a median depression; antennal insertions in lateral position relative to the antefrons, not aligned with front ocellus; a strong sulcus between frons and vertex; posterior ocelli on a high gibbosity well separated from others by strong depressions; lateral sulci between ocelli and lateral sides of vertex complete and reaching posterior sulcus of the vertex; suture between vertex and occiput rather well pronounced. All legs preserved at least in part, with two rows of strong spines on femora and tibiae; protibial comb absent; profemur 1.3 mm in length, protibia c. 1.6 mm in length; mesofemur 1.8 mm in length, mesotibia 1.7 mm in length, tarsi 0.4 mm in length; metafemur 3.1 mm in length, metatibia not preserved; three tarsomeres on all legs. Lateral neck structure of arrester system sensu Gorb (1998) well visible (arrester system present) ( Fig. 12
View Figure 12
); prothorax with notal anterior lobe narrow but rather pronounced anterior margin, median notal lobe broad, with two low lateral gibbosities separated by a median depression, posterior notal lobe well defined, erected and in dorsal view bearing a small triangular lug at median part of distal border ( Figs 5
View Figure 5
, 12
View Figure 12
); area constituted by anterior margin of pterothorax and collar crests delimiting a well-defined triangle, larger than in
Hemiphlebia
( Fig. 5
View Figure 5
); pterothorax of zygopterid type, distinctly higher than wide, 2.7 mm high, 2.0 mm wide; interpleural suture only present around metastigmal area, 0.3 mm in length, dorsal part absent.
Discussion: The presence of long and slender raptorial legs, with femoral spines similar to the tibial spines, and the reduction of the terminal kink of CP at the nodus are apomorphies of
Zygoptera ( Bechly, 1996)
. The transverse elongation, the dorsoventral median compression of the head capsule, and distance between the compound eyes of
Electrohemiphlebia barucheli
gen. et sp. nov. are comparable to those of many
Zygoptera
. The well-pronounced cephalic sulcus between the frons and vertex, as in
Hemiphlebia
( Figs 4
View Figure 4
, 16
View Figure 16
), is a feature unlike most
Zygoptera
.
Within the
Zygoptera
few taxa have so dissimilar discoidal cells in the fore- and hindwing, i.e. with the cell basally opened and with anterodistal part nearly straight in the forewing, but basally closed and with strong angles between the anterior and distal sides in the hindwing. This is especially true for the Recent Australian genera
Hemiphlebia Selys, 1868
(
Hemiphlebiidae Tillyard, 1926
) and
Chorismagrion Morton, 1914
(
Chorismagrionidae Tillyard & Fraser, 1938
), and also the Early Cenozoic family
Frenguelliidae Petrulevičius & Nel, 2003
( Petrulevičius & Nel, 2003, 2007). The latter strongly differs from
Electrohemiphlebia
in the bases of RP3/4 and IR2 being well basal of the nodus and in having a very different, highly specialized nodus.
Chorismagrion
differs from
Electrohemiphlebia
in that its postnodal and postsubnodal cross-veins are aligned, the wings have a long petiole, and the arculus is just distal to Ax2 ( Münz, 1919).
Electrohemiphlebia
differs from
Hemiphlebia
in AA separating from AP very close to the wing base, instead of close to the level of CuP, and the vertical subnodus.
Bechly (1996), after Kennedy (1919), proposed as a synapomorphy of
Hemiphlebia
the obsolescence of the protibial comb, a feature also seen in
Electrohemiphlebia
( Figs 6
View Figure 6
, 17
View Figure 17
). Furthermore,
Electrohemiphlebia
and
Hemiphlebia
share the presence of a sulcus between the frons and vertex; posterior ocelli positioned on pronounced gibbosities (although certainly more pronounced in
Electrohemiphlebia
than in
Hemiphlebia
); and complete and deep sulci between ocelli, ocellar gibbosities, and lateral sides of postfrons (see Figs 5
View Figure 5
, 15
View Figure 15
) ( Fraser, 1955). In the great majority of other recent
Zygoptera
the posterior ocelli are not placed on such pronounced gibbosities. There are no clear sulci between the ocelli and the lateral parts of the vertex, except in a few recent taxa (
Synlestes
). Such sulci are present in the
Tarsophlebiidae
, sister group of (
Zygoptera
+
Epiproctophora
) (visible in a specimen from China, Huang & Nel, 2009), but also in the
Epiproctophora
themselves (
Epiophlebia
and the Anisoptera). Accordingly, they are probable plesiomorphies of the taxa considered herein.
Electrohemiphlebia
and
Hemiphlebia
View in CoL
also share a strongly reduced thoracic interpleural suture (only present in the metastigmal area in
Electrohemiphlebia
, but also present in the dorsal one-tenth in
Hemiphlebia
View in CoL
) ( Asahina, 1957). Trueman (1999) considered the open discoidal cell of the forewing in
Hemiphlebia
View in CoL
to be ‘derived with respect to the closed condition in Zygoptera’. This character could be considered a synapomorphy of
Electrohemiphlebia
and
Hemiphlebia
View in CoL
, but it is also present in some other
Zygoptera
that are not related to
Hemiphlebia
View in CoL
. Further characters shared by
Electrohemiphlebia
and
Hemiphlebia
View in CoL
are as follows: postnodal and postsubnodal cross-veins not aligned (a symplesiomorphy after Bechly, 1998b); bases of RP3/4 and IR2 opposite the subnodus; CuA strongly zigzagged; arculus distinctly distal to Ax2, not opposite it; no secondary antenodal cross-veins; area between RA and RP broadened at level of base of RP3/4; all intercalary veins (except IR1? and IR2) suppressed (potential synapomorphy after Bechly, 1998b), petioles of wing base relatively reduced (potential synapomorphy after Bechly, 1998b).
Bechly (1998b) considered that the Early Cretaceous genus
Parahemiphlebia Jarzembowski et al. (1998)
was a hemiphlebiid, and that the other Early Cretaceous genus
Cretarchistigma Jarzembowski et al. (1998)
could also belong to this family.
Electrohemiphlebia
shares with both of these genera a similar pattern in the wing base, with AA separating from AP near the wing base, and two long cells in the anal area, in addition to similar overall patterns in the wing venation.
Electrohemiphlebia
differs from both
Cretarchistigma
and
Parahemiphlebia
in that the subnodus is vertical, rather than of more typical obliquity. A vertical subnodus is not frequent among
Zygoptera
, convergently present in two fossil clades, the
Sieblosiidae
and Dysagrioninae.
Electrohemiphlebia
differs also from
Cretarchistigma
in that the hindwing discoidal cell has its anterior margin distinctly shorter than the distal margin Jarzembowski et al. (1998).
Parahemiphlebia
comprises three species –
Parahemiphlebia cretacica Jarzembowski et al., 1998
,
Parahemiphlebia mickoleiti Bechly, 1998b
(both from the Late Aptian, Crato Formation of north-eastern Brazil), and
Parahemiphlebia allendaviesi Jarzembowski et al., 1998
(Berriasian Purbeck Group of the UK). The differences between the preserved and comparable wing venational structures of
Electrohemiphlebia
and these three species are few and at most of specific importance. In
P. allendaviesi
, the hindwing discoidal cell is shorter than in
Electrohemiphlebia
. The wings of
P. mickoleiti
are exceedingly short, 9 mm in length, and distinctly shorter than those of
Electrohemiphlebia
. Distances from the base to the nodus are 3.7 mm in
P. mickoleiti
, 6.6 mm in
P. cretacica
, 5.3 mm in
P. allendaviesi
, and 4.5 mm in
Electrohemiphlebia
. Thus
Electrohemiphlebia
is only slightly larger than the smallest damselfly,
P. mickoleiti
. Lastly,
Electrohemiphlebia
differs from
P. cretacica
and
P. mickoleiti
in the distinctly narrower discoidal cell, with a more acute angle between MAb and MP + CuA (condition unknown for
P. allendaviesi
).
The discovery of
Electrohemiphlebia
confirms the former attribution of the genus
Parahemiphlebia
(based on wing venation only) to the
Hemiphlebiidae
and the very wide distribution ( Brazil, UK, France, Jordan) of this family during the Cretaceous.
