Nasiornis messelornithoides nov. gen., nov. sp.; Parvirallus incertus nov. sp.; Walbeckornis waltonensis nov. sp. (1 Viewer)

[Fred Ruhe]

Gerald Mayr & Andrew C. Kitchener, in press

Messelornithids and messelornithid-like birds from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK)

Geobios (in press).
doi:10.1016/j.geobios.2023.12.011. ISSN 0016-6995.

Abstract and free pdf: https://www.sciencedirect.com/science/article/pii/S0016699524000421

We describe gruiform and gruiform-like birds from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK). One species belongs to the Messelornithidae and is classified as Nasiornis messelornithoides nov. gen., nov. sp.; the coracoid of this species resembles that of Bumbaniralla from the early Eocene of Mongolia. Another possible messelornithid species is tentatively assigned to the poorly known taxon Parvirallus Harrison and Walker, 1979, as ?P. incertus nov. sp. A further species is referred to the taxon Walbeckornis Mayr, 2007, as W. waltonensis nov. sp., and extends the geographical and temporal range of this taxon, which so far was only known from the Paleocene of Germany. Even though similarities between Walbeckornis and messelornithids were previously noted, a plesiomorphic morphology of the quadrate suggests a position of Walbeckornis outside crown group Gruiformes. Furthermore, all fossil taxa described in the present study lack a deeply concave facies articularis alularis (carpometacarpus), which we identify as a previously overlooked apomorphy of crown group Ralloidea. Therefore, resemblances between Walbeckornis and the Messelornithidae, which are the sister taxon of crown group Ralloidea, are likely to be plesiomorphic for a more inclusive clade.

Enjoy,

Fred

 

[Fred Ruhe]

Systematic paleontology

Aves Linnaeus, 1758
Gruiformes Bonaparte, 1854
Ralloidea Vigors, 1825
Messelornithidae Hesse, 1988

Emended diagnosis: Small to medium-sized “rail-like” birds with short wings and long legs that are characterized by a coracoid with a foramen nervi supracoracoidei and a crista procoracoidei; an ulna that is subequal to the humerus in length; a carpometacarpus with a ventrally directed tubercle on the proximal portion of the os metacarpale minus; a femur with a mediolaterally wide distal end (as wide as the distal end of the humerus); a hypotarsus with
two dorsoplantarly stacked canals (presumably for the tendons of musculus flexor digitorum longus and m. flexor perforans et perforatus digiti 2); a short trochlea metatarsi II that reaches
only to the base of the trochlea metatarsi IV.

Genus Nasiornis nov. gen.

Derivation of the name: From nasus (Lat.): nose, in reference to the use of “Naze” (semantically related to “nose”) in the name of the type locality, and ornis (Gr.): bird.

Type species: Nasiornis messelornithoides nov. gen., nov. sp.

Differential diagnosis: Differs from Messelornis Hesse, 1988 in that the foramen nervi supracoracoidei of the coracoid is situated closer to the cotyla scapularis and the crista procoracoidei is less developed (even though a part of the crista appears to be broken in NMS.Z.2021.40.99); the scapula has a longer and more pointed acromion. Distinguished from Pellornis Bertelli et al., 2011 in that the foramen nervi supracoracoidei (coracoid) is situated closer to the cotyla scapularis (the foramen itself is not visible in the Pellornis mikkelseni holotype, but the exposed portion of the shaft shows that it was not situated in the same position as in the new taxon) and in that the cotyla scapularis has a more circular outline; the scapula has a longer and more pointed acromion; the tuberculum dorsale of the humerus is proximodistally more elongated. Differs from Itardiornis Mourer-Chauviré, 1988 in that the coracoid has a cup-shaped cotyla scapularis (shallow facies articularis scapularis in I. hessae); the processus flexorius of the humerus is proximodistally narrower. Distinguished from Bumbaniralla Zelenkov, 2021 in that the facies articularis humeralis of the coracoid is less strongly laterally protruding and the facies articularis clavicularis has a better developed ventral portion. Differs from Coturnipes Harrison and Walker, 1977 in that the trochlea metatarsi II is shorter (reaching to the base of the trochlea metatarsi IV, whereas it reaches to the middle of this trochlea in C. cooperi). Distinguished from Parvirallus Harrison and Walker, 1979 in that the tuberculum supracondylare dorsale of the distal humerus is situated farther distally; the processus flexorius is more ventrally protruding; the incisura intercondylaris forms a less deeply incised notch in the distal margin of the humerus.

Nasiornis messelornithoides nov. gen., nov. sp.

Derivation of the name: The species epithet refers to the similarity of the new species to the taxon Messelornis

Holotype: NMS.Z.2021.40.99 (including several vertebrae including the pygostyle, fragments of some ribs, extremitas omalis of right coracoid, fragmentary extremitas omalis of left coracoid, cranial portion of left scapula, proximal portion of right humerus, distal portions of both humeri, left ulna, distal portion of right ulna, right and partial left radius, proximal and distal portions of left radius, left carpometacarpus, proximal end of left femur, distal end of right femur, and proximal end of left tibiotarsus; Fig. 2(A)); collected in 1986 by M. Daniels (original collector’s number WN 86546

Type locality and horizon: Walton-on-the-Naze, Essex, United Kingdom; Walton Mb. of the London Clay Fm. (previously Division A2; Jolley, 1996; Rayner et al., 2009; Aldiss, 2012), early Eocene (early Ypresian, 54.6‒55 Ma; Collinson et al., 2016).).

Referred specimen: NMS.Z.2021.40.101 (including proximal end of left humerus, distal end of right humerus, proximal and distal ends of right ulna, distal ends of left tibiotarsus and tarsometatarsus, several pedal phalanges, as well as various bone fragments; Fig. 2(B)); collected in 1987 by M. Daniels (original collector’s number WN 87567A).

Tentatively referred specimen: NMS.Z.2021.40.100 (including right tarsometatarsus and several pedal phalanges; Fig. 2(C)); collected in 1985 by M. Daniels (original collector’s number WN 85503).

Measurements (maximum length, in mm): NMS.Z.2021.40.99: right humerus, distal width, 7.5; right ulna, 33.1; right radius, 33.8; left carpometacarpus, 22.0. NMS.Z.2021.40.101: right humerus, distal width, 7.2; left tibiotarsus, distal width, 4.5; right tarsometatarsus, distal width, 5.0. NMS.Z.2021.40.100: right tarsometatarsus, length, 37.4, proximal width, 4.4, distal width, 4.6.

With a length of 37.4 mm, the tentatively referred tarsometatarsus NMS.Z.2021.40.100 is only slightly longer than the ulna of NMS.Z.2021.40.99, which measures 33.1 mm. The tarsometatarsus of Messelornis cristata is about 1.5 times longer than the ulna (Hesse, 1990; Table 1), but the species shows a significant variation in bone dimensions and was hypothesised to be sexually dimorphic in size (Hesse, 1990). Therefore, we consider it highly possible that NMS.Z.2021.40.100 represents a small individual (possibly a female) of N. messelornithoides nov. gen., nov. sp. and tentatively assign the specimen to this species.

Diagnosis: As for the genus, by monotypy.

Remarks: The tentatively referred tarsometatarsus S.Z.2021.40.100 differs from that of Messelornis cristata, Pellornis mikkelseni, and Itardiornis hessae in that it lacks an ossified arcus extensorius (the condition in M. nearctica is unknown); the bone is furthermore
distinguished from the tarsometatarsus of P. mikkelseni in that the hypotarsus is more plantarly protruding and from that of I. hessae in its much smaller size (proximal width 4.4 mm vs. 7.5 mm). With a distal tibiotarsus width of 4.6 mm (NMS.Z.2021.40.101), the
new species is larger than “Parvirallus” medius (distal width of tibiotarsus 3.9 mm; Harrison, 1984) and “P.” gassoni (distal width of tibiotarsus 2.5 mm; Harrison, 1984), and smaller than “P.” bassetti (distal width of tibiotarsus 6.2 mm; Harrison, 1984).

Fred


Fig. 1. Messelornithids and messelornithid-like birds from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK). A-C. Nasiornis messelornithoides nov. gen., nov. sp. (Messelornithidae). A: holotype, NMS.Z.2021.40.99; B: NMS.Z.2021.40.101). The arrow
denotes an enlarged detail of the os metatarsale I; C: tentatively referred specimen, NMS.Z.2021.40.100. D. ?Parvirallus incertus nov. sp. (cf. Messelornithidae), holotype, NMS.Z.2021.40.102. E. ?P. incertus nov. sp. (cf. Messelornithidae), NMS.Z.2021.40.103. F.
Walbeckornis waltonensis nov. sp. (fam. incert. sed.), holotype, NMS.Z.2021.40.104. Abbreviation: pat, processus articularis tarsometatarsalis. Scale bars: 10 mm.

 

[Fred Ruhe]

?Messelornithidae Hesse, 1988
Genus ?Parvirallus Harrison and Walker, 1979

Remarks: The taxon Parvirallus was originally established by Harrison and Walker (1979) for Parvirallus gracilis from the middle Eocene (Bartonian) of Lee-on-Solent, Hampshire (UK); this species was assigned to the Rallidae and is only known from the distal end of a humerus. Three species of Parvirallus (P. bassetti, P. medius, and P. gassoni) were subsequently described by Harrison (1984) from the Isle of Sheppey and are based on distal tibiotarsi. Owing to the lack of overlap in the bones, an assignment of these specimens to Parvirallus is highly speculative.
Therefore, the single bone that can be unambiguously assigned to the taxon Parvirallus is the distal humerus of P. gracilis. The similar size and morphology of this bone to the distal humerus of the new species described below suggest close affinities, which is supported
further as the fossils stem from geographically proximate localities. However, owing to some morphological differences (see differential diagnosis below), our classification of the new species into the taxon Parvirallus is tentative.
The assignment of Parvirallus to the Rallidae was not properly justified by Harrison and Walker (1979) and Harrison (1984), and the taxon was largely ignored by subsequent authors. Parvirallus has not yet been compared with the Messelornithidae, which it resembles in the morphology of the distal humerus. Because messelornithids are the dominant “rail-like” gruiform birds in the middle Eocene of Europe (Mayr, 2022) and because the new fossil
described below combines a Parvirallus-like distal humerus with a messelornithid-like morphology of the wing and pectoral girdle bones, we consider messelornithid affinities of Parvirallus possible, if not likely.

?Parvirallus incertus nov. sp.
Fig. 2(D, E)

Derivation of the name: The species epithet is derived from incertus (Lat.): uncertain and refers to the taxonomic and phylogenetic affinities of the new species.

Holotype: NMS.Z.2021.40.102 (including partial skeleton including right coracoid, extremitas omalis of left coracoid, left scapula, fragments of right scapula, right humerus, distal portion of left humerus, right ulna, proximal end of left ulna, left radius, and left
carpometacarpus; Fig. 2(D)); collected in 1996 by M. Daniels (original collector’s number WN 96930).

Type locality and horizon: Walton-on-the-Naze, Essex, United Kingdom; Walton Mb. of the London Clay Fm., early Eocene (early Ypresian).

Referred specimen: NMS.Z.2021.40.103) (extremitas omalis of right coracoid; Fig. 2(E)); collected in 1989 by M. Daniels (original collector’s number WN 89632).

Measurements (maximum length, in mm): NMS.Z.2021.40.102: right coracoid, 16.8; right humerus, 24.7; right ulna, 25.0; left radius, 23.0; left carpometacarpus, 14.7.

Differential diagnosis: Slightly smaller than Parvirallus gracilis Harrison and Walker, 1979 (distal width of humerus 5.0 mm vs. 5.4 mm in P. gracilis); the tuberculum supracondylare dorsale (humerus) is more sharply delimited; the condylus dorsalis is smaller. Differs from Messelornis, Pellornis, and Nasiornis in that the tuberculum dorsale of the humerus is proximodistally longer; the ulna is slightly longer than the humerus; the olecranon is much
more pronounced; furthermore distinguished from Nasiornis in that the foramen nervi supracoracoidei (coracoid) is situated farther sternally. Differs from Songzia Hou, 1990 in that the coracoid is proportionally longer (ratio humerus to coracoid 1.47 vs. 1.72‒1.91 in S. acutunguis); the crista deltopectoralis (humerus) is proportionally shorter; the condylus dorsalis of the humerus is proportionally smaller; and the ulna is slightly longer than the
humerus (as long as the humerus in Songzia). Distinguished from Bumbaniralla Zelenkov, 2021 in that the foramen nervi supracoracoidei (coracoid) is situated farther away from the
cotyla scapularis. Differs from crown group Ralloidea in that the humerus has a larger proximal end; the facies articularis alularis of the carpometacarpus is not markedly concave.

Fred

 

[Fred Ruhe]

Familia incertae sedis
Genus Walbeckornis Mayr, 2007
Walbeckornis waltonensis nov. sp.
Fig. 2(F)

Derivation of the name: The species epithet refers to the type locality

Holotype: NMS.Z.2021.40.104 (including partial skull and mandible, partial right quadrate, partial ?left pterygoid, parts of the hyoid apparatus, several vertebrae, right and partial left coracoid, right scapula lacking caudal end, partial left humerus, distal portion of right humerus, distal portion of right ulna, proximal ends of both radii, fragments of left and right carpometacarpi, partial left femur, distal portion of right femur, proximal and distal portions of left tibiotarsus, fragments of right tibiotarsus, partial ?left fibula, distal end of right tarsometatarsus, and pedal phalanges; Fig. 2(F)); collected in 1985 by M. Daniels (original collector’s number WN 85505).

Type locality and horizon: Walton-on-the-Naze, Essex, United Kingdom; Walton Mb. of the London Clay Fm., early Eocene (early Ypresian).

Measurements (in mm): Mandible, length, 36.4; right coracoid, maximum length, 21.9; left humerus, length, 36.1; right humerus, distal width, 7.0; left tibiotarsus, distal width, 5.3; right tarsometatarsus, distal width, 5.4.

Differential diagnosis: Differs from Walbeckornis creber Mayr, 2007 in that the foramen nervi supracoracoidei is situated closer to the medial margin of the coracoid; the tuberculum supracondylare dorsale on the distal humerus is situated farther proximally; the pons supratendineus of the tibiotarsus is proximodistally broader. Distinguished from Nasiornis messelornithoides in that the distal portion of the caudal rim of the trochlea carpalis (carpometacarpus) forms a distinct step; the distal end of the femur is proportionally narrower (much narrower than the distal end of the humerus, whereas the distal humerus and distal femur are of subequal width in N. messelornithoides); the trochlea metatarsi II is longer (reaching to the middle of the trochlea metatarsi IV); the foramen vasculare distale is situated farther distally. Differs from Messelornis Hesse, 1988 in that the coracoid lacks a pronounced
crista procoracoidei; the femur has proportionally narrower distal end; the trochlea metatarsi II reaches farther distally; the pedal phalanges have wider proximal portions. Distinguished
from Pellornis mikkelseni Bertelli et al., 2011 in that the tuberculum dorsale of the humerus is longer and the processus extensorius of the carpometacarpus is proportionally shorter and less strongly cranially protruding. Distinguished from Parvirallus gracilis Harrison and Walker, 1979 in that the dorsal margin of the distal humerus is straighter (more concave in P. gracilis); furthermore distinguished from ?Parvirallus incertus in that the crista deltopectoralis is proportionally longer and the extremitas omalis of the coracoid is
proportionally longer. Differs from Precursor litorum Harrison and Walker, 1977 in that the condylus dorsalis of the humerus is less inclined relative to the longitudinal axis of the humerus. Differs from Coturnipes cooperi Harrison and Walker, 1977 in that the dorsal opening of the foramen vasculare distale is smaller; the trochlea metatarsi II is proportionally larger. Differential diagnosis: Differs from Walbeckornis creber Mayr, 2007 in that the foramen
nervi supracoracoidei is situated closer to the medial margin of the coracoid; the tuberculum supracondylare dorsale on the distal humerus is situated farther proximally; the pons supratendineus of the tibiotarsus is proximodistally broader. Distinguished from Nasiornis messelornithoides in that the distal portion of the caudal rim of the trochlea carpalis (carpometacarpus) forms a distinct step; the distal end of the femur is proportionally narrower
(much narrower than the distal end of the humerus, whereas the distal humerus and distal femur are of subequal width in N. messelornithoides); the trochlea metatarsi II is longer (reaching to the middle of the trochlea metatarsi IV); the foramen vasculare distale is situated farther distally. Differs from Messelornis Hesse, 1988 in that the coracoid lacks a pronounced crista procoracoidei; the femur has proportionally narrower distal end; the trochlea metatarsi II reaches farther distally; the pedal phalanges have wider proximal portions. Distinguished from Pellornis mikkelseni Bertelli et , 2011 in that the tuberculum dorsale of the humerus is
longer and the processus extensorius of the carpometacarpus is proportionally shorter and less strongly cranially protruding. Distinguished from Parvirallus gracilis Harrison and Walker, 1979 in that the dorsal margin of the distal humerus is straighter (more concave in P. gracilis); furthermore distinguished from ?Parvirallus incertus in that the crista deltopectoralis is proportionally longer and the extremitas omalis of the coracoid is proportionally longer. Differs from Precursor litorum Harrison and Walker, 1977 in that the condylus dorsalis of the humerus is less inclined relative to the longitudinal axis of the humerus. Differs from Coturnipes cooperi Harrison and Walker, 1977 in that the dorsal opening of the foramen vasculare distale is smaller; the trochlea metatarsi II is proportionally larger.

Fred