Two new long-rostrum cranefly species from the Cretaceous Iberian amber (Diptera, Limoniidae, Helius)

First record of the genus Helius—long-rostrum cranefly from Maestrazgo Basin (eastern Spain, Iberian Penisula) is documented. Two new fossil species of the genus Helius are described from Cretaceous Spanish amber and compared with other species of the genus known from fossil record with particular references to these known from Cretaceous period. Helius turolensis sp. nov. is described from San Just amber (Lower Cretaceous, upper Albian) Maestrazgo Basin, eastern Spain, and Helius hispanicus sp. nov. is described from Álava amber (Lower Cretaceous, upper Albian), Basque-Cantabrian Basin, northern Spain. The specific body morphology of representatives of the genus Helius preserved in Spanish amber was discussed in relation to the environmental conditions of the Maestrazgo Basin and Basque-Cantabrian Basin in Cretaceous.

. List of all fossil species belonging to genus Helius, with age and localities.     Diagnosis. Rostrum only slightly longer than head, constitute 0.5 the length of head; antenna relatively slender and short, terminate just beyond the head, each flagellomere with two very elongate setae, approximately 6.7 times longer than length of segments bearing them; palpus longer than rostrum; last palpomere elongate, slender, longer than palpomeres 1-3 combined; third palpomere widened in basal part, about 0.3 × the length of the fourth palpomere.
Etymology. The specific epithet is derived from Teruel, where the specimen was been found.
Horizon and locality. The specimen was found in amber from gray-black claystones with abundant plant remains which corresponds to a deposit of a fluvial deltaic swamp, in the Utrillas Group 33 , Lower Cretaceous, upper Albian. The outcrop of San Just 34 is located in the Maestrazgo Basin, municipality of Utrillas (Province of Teruel, Aragón Autonomous Community, eastern Spain).
Description. Body ( Fig. 2A)   www.nature.com/scientificreports/ 0.51 mm long (1/0.05 mm; 2/0.07 mm; 3/0.12 mm; 4/0.27 mm) slender, two basal segments almost equal in length, only slightly widened at distal part, third palpomere massive, longer than first and second palpomeres, but shorter than first and second palpomeres combined, widened at basal part and narrowed at distal part, fourth palpomere very elongate, longer than all other palpomeres arranged together, tiny. Thorax ( Fig. 2A): wing (Figs. 1B, 2A,C) 3.65 mm long, 0.93 mm wide; pterostigma present, oval, pale-brown; Sc relatively short, ends well before fork of Rs; Rs relatively short, R 2+3+4 almost 1.5 × the length of Rs; R 1 ends opposite 0.60 × length of R 2+3+4 level; R 5 longer than R 2+3+4 ; cross-vein m-cu connected with M 3+4 behind half of its length measured from fork of Mb; d-cell, twice longer than wide; M 3 slightly waved, 1.5 × as long as d-cell; A 1 and A 2 slightly waved, arched at the margin of wing, A 1 elongate. Tip of A 1 behind Rb bifurcation level.
Abdomen: hypopygium (Figs. 1D, 2A,B): 0.66 mm long, with gonocoxite relatively narrow and elongate, approximately 3 × as long as wide; at the apex of gonocoxite bunch of very elongate setae arranged around the tip; outer and inner gonostyles of comparable size; outer gonostylus elongate, slightly widened in the distal part.
Comparison. Helius turolensis sp. nov. differs from all other Cretaceous representatives of genus by the ratio between the length of rostrum, antenna, palpus and head. This species differs from species known from the Eocene and the Miocene periods by tiny, slender antennae with characteristic, very elongate setae on each flagellomere, 6.7 × longer than length of segments bearing them.
Moreover, in contrast to H. hispanicus sp. nov. third palpomere is massive and widened at the base, in H. turolensis sp. nov. this palpomere is very small, not longer than 1.5 × its width.
The antennae of H. turolensis sp. nov. bears two very elongate, symmetrically arranged setae, similarly to H. hispanicus sp. nov. In contrast to H. hispanicus sp. nov. in H. turolensis sp. nov. palpus is more slender, last palpomere is elongate and tiny, longer than the length of all other palpomeres combined in H. hispanicus sp. nov. last palpomere is not very elongate approximately as long as second and third combined. Differences are also well visible in ratio between the length of rostrum, antenna, palpus and head between these two species.
In H. turolensis sp. nov. palpus is longer than rostrum, antenna is almost 0.25 × longer than palpus, while in H. hispanicus sp. nov. palpus and rostrum are in length, antenna is almost 0.14 × longer than palpus.
In In contrast to other Cretaceous species H. turolensis differs especially by morphology of the head, the wing venation and the male genitalia.
In H. ewa, rostrum is very elongate, reaching about the third of body length, in H. turolensis rostrum is only slightly longer than head, head ca. 0.36 mm long; rostrum ca. 0.38 mm long. In H. lebanensis, discal cell is opened, in contrast to H. turolensis where discall cell is closed. In H. krzeminskii, rostrum is relatively short and the differences between these two species are well visible comparing the ratio of the length of rostrum, the length of head and head appendages. In H. botswanensis palpus, is shorter than rostrum, rostrum is approximately twice as long as head, while in H. turolensis, palpus is longer than rostrum, rostrum is approximately as long as the head.
Diagnosis. Rostrum only slightly longer than head; antennomeres 1-4 relatively massive and short, terminate just beyond the head; each flagellomere with two very elongate setae, approximately 4.5 × longer than segments bearing them; palpus as long as rostrum; last palpomere not very elongate approximately as long as second and third; penultimate palpomere very small and short, about 0.25 × the length of the fourth palpomere.
Etymology. The specific epithet is derived from Hispania, Latin name for Spain.  (Fig. 3A) (1/0.43 mm; 2/0.22 mm; 16/0.10 mm); scape cylindrical, but wide and massive, elongate, 2.5 × longer than wide, with a few not very elongate setae; pedicel relatively elongate and wide, massive, widened in distal part, longer than wide; first flagellomere wide, relatively short, flagellomeres 1-14 tapering toward apex; each flagellomere with two symmetrically arranged very long setae, much longer than segments bearing them, last flagellomere with two very elongate setae arranged at the tip since the last it's the one at the tip. Maxillary palp (Figs. 3B, 4A-C) four-segmented, two basal segments massive, relatively elongate and almost equal in length (length of palpomeres 0.59 mm: 1/0.14; 2/0.14 mm; 3/0.07 mm; 4/0.24 mm), third On the antennae of this species occur two very elongate, symmetrically arranged setae, these very elongate setae does not occur in other species of Helius known from fossil record of younger periods like Eocene.

Discussion
Six species of flies belonging to the genus Helius are known from the cretaceous period and only three are known from Spanish amber 1-3 (Fig. 5). All the species of the genus Helius described so far on the basis of inclusions in Cretaceous Spanish amber came from the same outcrop Peñacerrada I, Álava, Basque-Cantabrian Basin, Spain.
One of the species new to science included in this work, H. hispanicus sp. nov., was described on the basis of inclusions also originating from the outcrop Peñacerrada I, Álava, while the other fossil representative H. turolensis sp. nov. was found at the outcrop of Sun Just located in the Maestrazgo Basin. Both the first and second positions are dated to upper Albian. It should be noted that this is the first record of the genus Helius from fossil record of the Maestrazgo Basin.
Most of the 150 Iberian Penisula amber deposits are dated to Albian (Early Cretaceous), only a few of these localities are dated to Late Cretaceous e.g. in Asturias or Catalonia, and only two localities with amber are dated to the late Triassic (both in Alicante) 35 .
Both Basque-Cantabrian Basin and Maestrazgo Basin were formed during significant changes in fauna and flora on earth. The large sedimentary Basque-Cantabrian Basin has developed between the Iberian and European www.nature.com/scientificreports/ tectonic plates, the Maestrazgo basin is an intercontinental basin located in the Iberian Range 35 . In the Basque-Cantabrian Basin amber is preserved in rocks rich in organic matter from sediments, is large quantity of plants remains, coal and other continental organic material which was transported by rivers. Largest deposits of Maestrazgo Basin is San Just with abundant plant remains and fusinished wood, were probably formed during subtropical hot-humid environment with hot and dry areas 35 .
It is in such an area with a subtropical, hot and humid environment and dry areas that the representatives of the genus Helius occurred in Cretaceous period.  www.nature.com/scientificreports/

Funding
Open Access funding enabled and organized by the University of Rzeszów.