Late Oligocene birds from Poland

A new passerine (Aves: Passeriformes) and three other specimens of Late Oligocene birds from Poland, with a review of all Paleogene birds from the northern part of the Carpathian Arc

Zbigniew M. Bochenski, Teresa Tomek, Robert Szybiak, and Krzysztof Wertz

Article number: 29.2.a26
https://doi.org/10.26879/1712
Copyright Society of Vertebrate Paleontology, June 2026

Author biographies
Plain-language and multi-lingual abstracts
PDF version
Appendix

Submission: 18 May 2026. Acceptance: 10 June 2026.

ABSTRACT

This paper describes four incomplete specimens from the Late Oligocene deposits of Poland. One of these, containing highly diagnostic bones, is described as a new species of Suboscines within Passeriformes, another likely also belongs to Suboscines, and the remaining two, although they possess articulated elements, are too poorly preserved to be assigned to any bird group and have been identified as Aves indet. To date, all new passerine taxa from the Paleogene of Europe have been found in Early Oligocene (Rupelian) deposits. Significantly fewer specimens are dated to the Late Oligocene (Chatian). The only passerine from this period with preserved articulated bones is a severely damaged foot; the remaining specimens consist of isolated bones. Therefore, the new passerine species described in this paper provides valuable data closer to the Neogene, helping to fill a gap in our knowledge and potentially documenting later stages of early passerine evolution. Its scientific value is all the greater because it has associated bones that may be helpful in future phylogenetic studies. The manuscript also summarizes our knowledge of Oligocene birds from the northern part of the Carpathian Arc. In addition to the numerically dominant Passeriformes, representatives of the Procellariiformes, Upupiformes, Galliformes, Ralloidea, Apodiformes, Accipitriformes, and Piciformes are also known. Recent research has shown that the deposits from the Jamna Dolna 2 site, originally dated to the Early Oligocene, actually date to the Late Oligocene, which requires a correction of the ages of several previously described bird species.

Zbigniew M. Bochenski. Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Slawkowska 17, 31-016 Krakow, Poland, corresponding author. [email protected]
Teresa Tomek. Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Slawkowska 17, 31-016 Krakow, Poland. [email protected]
Robert Szybiak. Muzeum Skamieniałości i Minerałów w Dubiecku, Krasickiego 3a, 37-750 Dubiecko, Poland. [email protected]
Krzysztof Wertz. Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Slawkowska 17, 31-016 Krakow, Poland, corresponding author. [email protected]

Keywords: fossil birds; new genus; new species; Carpathian flysch; Palaeogene

Final citation: Bochenski, Zbigniew M., Tomek, Teresa, Szybiak, Robert, and Wertz, Krzysztof. 2026. A new passerine (Aves: Passeriformes) and three other specimens of Late Oligocene birds from Poland, with a review of all Paleogene birds from the northern part of the Carpathian Arc. Palaeontologia Electronica, 29(2):a26.
https://doi.org/10.26879/1712
palaeo-electronica.org/content/2026/5902-late-oligocene-birds-from-poland

Copyright: June 2026 Society of Vertebrate Paleontology.
This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
creativecommons.org/licenses/by/4.0

https://zoobank.org/D93E888F-DC5A-41BF-A907-1384D0199138

INTRODUCTION

Large parts of Central and Eastern Europe were covered by the Paratethys during the Oligocene. Marine sediments of southeastern Poland are known for their rich fish fauna, preserved thanks to the anoxic conditions at the bottom; fossils of other organisms are also found sporadically (Bienkowska-Wasiluk, 2010; Kotlarczyk et al., 2006). In this paper, we describe four additional incomplete bird specimens from this region.

The oldest unambiguous passerine fossils date from the Early Oligocene (ca. 34-30 Ma) in Europe, documenting the initial colonization and diversification of this bird group on the continent. To date, only five species have been formally described from the Paleogene: Wieslochia weissi from Germany, Jamna szybiaki, Crosnoornis nargizia, Resoviaornis jamrozi, and Winnicavis gorskii all from Poland, and one complete but unnamed specimen (NT-LBR-014) from France (Bochenski et al., 2011, 2013, 2018, 2021; Mayr and Manegold, 2004, 2006a; Riamon et al., 2020; Mayr, 2022). These articulated passerine specimens all date from the Early Oligocene and are mostly characterized by a mixture of characters typical of modern Oscines and Suboscines; only NT-LBR-014 and Crosnoornis were considered Suboscines in their original publications. Recent phylogenetic studies (Lowi-Merri et al., 2024) indicate that Jamna szybiaki is a sister lineage of crown Passeriformes while Wieslochia, Crosnoornis, and NT-LBR-0014 belong to Suboscines, and Resoviaornis to Oscines. Outside Europe, the only unambiguously identified Paleogene passerine fossils are Late Oligocene remains representing two extinct species: Sericuloides marynguyenae and Orthonyx kaldowinyeri, both from Australia (Nguyen, 2023; Nguyen et al., 2014).

This diversification of Oligocene passerines is also supported by finds of much less complete specimens. Mayr and Manegold (2006b) have already tentatively identified a distal wing resembling Suboscines from the Early Oligocene deposits of France. Isolated wing bones are known from the Late Oligocene sediments of Germany, indicating the coexistence of Oscines and Suboscines in Europe at that time (Manegold, 2008). Also, several isolated passerine bones have been found from the Oligocene deposits in France (Mourer-Chauviré, 2006; Mourer-Chauviré et al., 1989, 2004).

This paper describes four incomplete specimens from the Late Oligocene deposits of Poland. One of these, containing highly diagnostic bones, is described as a new species of Suboscines, another likely also belong to Suboscines, and two others, although they have articulated elements, are too poorly preserved to be assigned to any bird group and have been identified as Aves indet. Given the paucity of Paleogene passerine fossils, each new find - especially one represented by multiple bones from the same individual - potentially provides insights into their early diversification and morphological experiments.

MATERIAL AND METHODS

The analyzed material consists of four specimens preserved on slabs found at the Jamna Dolna 2 site, dated to the Late Oligocene (Bienkowska-Wasiluk et al., 2025). Three of these specimens consist of a slab and counterslab, while one consists of only one slab. The skeletal elements are preserved as a mixture of bone impressions and remnants of fossilized bone tissue. This allows for clearly visible bone outlines, but many fine details remain unrecognizable.

Osteological terminology follows Baumel and Witmer (1993). Dimensions are given in millimeters and represent the greatest length along the longitudinal axis of the bone. The fossils were compared with specimens from the osteological collection of the Institute of Systematics and Evolution of Animals of the Polish Academy of Sciences and with published data on the osteology of extant and fossil passerines (Acanthisittidae, Oscines, and Suboscines), as well as extinct Zygodactylidae, which are morphologically very similar to passerines (Mayr, 2022).

SYSTEMATIC PALEONTOLOGY

Class AVES Linnaeus, 1758
Order PASSERIFORMES Linnaeus, 1758
Suborder SUBOSCINES sensu Ericson et al., 2003
Family indeterminate
Genus JAMNINKAORNIS gen. nov.
zoobank.org/38C4B92B-2090-4AF2-97D3-C3499B8DC331

Type species. Jamninkaornis kencampbelli sp. nov.

Etymology. From Jamninka, the name of a local stream and valley near the type locality (Jamna Dolna 2, SE Poland), and Greek ὄρνις (ornis) meaning “bird”.

Remarks. The specimen shows typical features of Passeriformes including: (1) slender long and narrow coracoid and humerus; coracoid with (2) processus acrocoracoideus well developed and hooked, (3) processus lateralis short and rounded; humerus with (4) prominent processus flexorius that projects far distally, and (5) clearly visible processus supracondylaris dorsalis.

Differential diagnosis. A small passerine bird, similar in size to a red-capped manakin Ceratopipra mentalis.

The specimen differs from other passerines in a unique combination of the following characters: coracoid with (1) processus acrocoracoideus well-developed and hooked, (2) tuberculum brachiale strongly developed medially, (3) straight medial margin of the omal section, (4) processus procoracoideus strongly elongated and extending as far medially as the processus acrocoracoideus, (5) processus lateralis (sternal end) short and rounded; humerus with (6) straight shaft, (7) thin and slender shaft, (8) crista deltopectoralis about one-third of the total length of the bone and extending farther distally than the crista bicipitalis, (9) prominent processus flexorius with a straight dorsal edge, (10) processus supracondylaris dorsalis: single and well-developed; (11) humerus:coracoid ratio equals 1.3.

Jamninkaornis kencampbelli differs from extant Acanthisittidae in characters # 1, 4, and 6. Character (4) distinguishes it from all extant Oscines. Although characters # 2, 4, 9 occur in extant Suboscines - both Eurylaimides (Old World suboscines) and Tyrannides (New World suboscines) - they can be excluded because none of the extant species examined exhibits the full set of these characters; this is also supported by geographic and temporal distance. Characters (3) and perhaps also 11 appear to be unique to J. kencampbelli.

Differences between Jamninkaornis kencampbelli and fossil taxa include the following characters: Primozygodactylus (1, 4, 5), Zygodactylus (1, 4), Wieslochia weissi (1, 3, 8), Crosnoornis nargizia (1, 3, 4, 7, 8, 11), NT-LBR-014 (1, 3, 11), Jamna szybiaki (1, 3, 7, 10, 11), Resoviaornis jamrozi (3, 4, 7, 8, 10, 11), Winnicavis gorskii (1, 3, 4, 7).

Jamninkaornis kencampbelli gen. et sp. nov.
zoobank.org/E83BEA9E-769A-404F-A1F3-29E634C22643

Etymology. The species is named in honour of Dr. Kenneth E. Campbell, Jr., American vertebrate paleontologist and ornithologist, longtime curator of fossil birds at the Natural History Museum of Los Angeles County, and one of the founders and first President of the Society of Avian Paleontology and Evolution (SAPE), in recognition of his contributions to paleontology, particularly his work on fossil bird taxonomy and evolution.

Holotype. MSMD Av JAM2_1a+b (Figure 1, Figure 2), right coracoid and right humerus preserved on two slabs, deposited at the Institute of Systematics and Evolution of Animals, PAS, Kraków, Poland.

Type locality and horizon. Jamna Dolna 2, ca. 20 km south-west of Przemyśl, in the area of the former village of Jamna Dolna, Podkarpackie Voivodeship, SE Poland. Chattian, Oligocene, ca. 26 MYA, Korzeniówka Member with ichthyofaunal zone IPM6, correlated with the nannoplankton of the NP25 zone (Bienkowska-Wasiluk et al., 2024, 2025).

Diagnosis. As for the genus.

Measurements. Measurements (in mm) taken from the main slab (A): coracoid: total length, 12.9, medial length, 12.5, sternal width, 3.3; humerus: total length, 16.6, proximal width, 4.6, distal width, 3.2, least shaft width, 1.5.

Description and Comparison

Coracoid. The coracoid on slab A is preserved primarily as an imprint of the ventral surface, with only the omal section showing bone fragments. On slab B, the ventral side is visible; the dorsal side faces the matrix. As in extant passerines and the Oligocene Resoviaornis jamrozi, the coracoid is long and slender, and the processus acrocoracoideus is well-developed and hooked; in Acanthisittidae, Primozygodactylus, Zygodactylus, Wieslochia weissi, Jamna szybiaki, Winnicavis gorskii, Crosnoornis nargizia, and NT-LBR-014, the processus acrocoracoideus was not hooked but straight or rounded (Bochenski et al., 2011, 2013, 2018, 2021; Mayr and Manegold, 2006a; Riamon et al., 2020). As in NT-LBR-014 and most extant Tyrannides, but unlike Eurylaimides, the tuberculum brachiale is strongly developed medially (Riamon et al., 2020). The medial margin of the omal section is roughly straight rather than curved as in extant and Oligocene Eupasseres; therefore, this appears to be a feature specific to Jamninkaornis kencampbelli. As in some extant Suboscines, Oligocene Wieslochia weissi and NT-LBR-014 the processus procoracoideus is strongly elongated and extends as far medially as the processus acrocoracoideus (Mayr and Manegold, 2006a, Riamon et al., 2020), in Winnicavis gorskii and Zygodactylidae the processus is only somewhat enlarged but does not reach as far medially (Bochenski et al., 2018; Smith et al., 2018); in extant Acanthisittidae, Oscines, and Oligocene Resoviaornis jamrozi and probably also in Crosnoornis nargizia the processus is reduced (Bochenski et al., 2013, 2021). The cotyla scapularis and facies articularis humeralis are not visible. As in Passeriformes, the processus lateralis (sternal end) is short and rounded; in Primozygodactylus it is laterally elongated (Mayr, 1998; Mayr and Zelenkov, 2009).

Humerus. The humerus on slab A is preserved primarily as an imprint of the caudal surface, with only the proximal and distal portions containing bone remnants. On plate B, only bone fragments of the proximal portion are present. The shaft is straight, not S-shaped as in Acanthisitti (see Riamon et al., 2020). It is also rather thin and slender, as in extant passerines and Wieslochia; in other Oligocene passerines (Jamna, Resoviaornis, Winnicavis, Crosnoornis) it was thick and massive (Bochenski et al., 2011, 2013, 2018, 2021; Mayr and Manegold, 2006a). As in Jamna, the crista deltopectoralis is about one-third of the total length of the bone and extends farther distally than the crista bicipitalis; in Wieslochia, Crosnoornis, and Resoviaornis, both cristae are shorter and extend equally far distally (Bochenski et al., 2011, 2013, 2021; Mayr and Manegold, 2006a). The processus flexorius has a straight dorsal edge (see Riamon et al., 2020: character #100), is very long, and projects significantly distally. The straight edge is common in Tyrannides; in Eurylaimides, the edge is usually deflected dorsocaudally (Riamon et al., 2020) although exceptions are known (Lowi-Merri et al., 2024). A prominent processus flexorius is also present in Wieslochia, Jamna, Resoviaornis, Crosnoornis, NT-LBR-014, and extant Passeriformes (Bochenski et al., 2011, 2013, 2021; Mayr and Manegold, 2006a; Riamon et al., 2020). As in NT-LBR-014 and many extant suboscines, the processus supracondylaris dorsalis is single and well-developed; in extant oscines it is often double (Riamon et al., 2020: characters #101 and 102) or it is equipped with additional cone-shaped projections (Manegold, 2008). In Jamna and Resoviaornis it was present but rather less developed (Bochenski et al., 2011, 2013).

Size and hum:cor ratio. Of all known Oligocene passerines, Jamninkaornis kencampbelli is closest in size to Crosnoornis; Resoviaornis was smaller, and Jamna, Winnicavis, Wieslochia, and NT-LBR-014 were larger (Bochenski et al., 2011, 2013, 2018, 2021; Mayr and Manegold, 2004, 2006a; Riamon et al., 2020). Among the extant Suboscines in the ISEZ PAN collection, Jamninkaornis kencampbelli is closest in size to Ceratopipra mentalis and Manacus vitellinus (Appendix). From all Oligocene and all 29 extant Suboscines from the ISEZ PAN collection, Jamninkaornis kencampbelli differs in the humerus:coracoid ratio (1.3 vs 1.0-1.2, respectively; Appendix).

cf. Suboscines sensu Ericson et al., 2003

Specimen MSMD Av JAM2_2 (Figure 3) is a skull of a small bird, preserved on a single slab. It was found at Jamna Dolna 2, SE Poland, and is dated to the Chattian (Oligocene, ca. 26 Ma), Korzeniówka Member, ichthyofaunal zone IPM6, correlated with the nannoplankton NP25 zone (Bienkowska-Wasiluk et al., 2024, 2025).

Measurements (in mm): reconstructed skull, 28.1 (as preserved, 25.8); reconstructed beak (nasofrontal hinge to tip), 12.3 (as preserved, 10.0); beak width at base, 7.2; length of narial openings, 6.3; width of braincase, 13.2; smallest interorbital width of the frontal bone, 2.9.

Remarks: The absolute dimensions of the skull and beak, as well as their shape and proportions, are similar to those of Wieslocha weissi from the Early Oligocene sediment (Mayr and Manegold, 2004, 2006a); the Early Oligocene woodpecker Rupelramphastoides knopfi had a significantly smaller skull and a relatively shorter beak (Mayr, 2006). The beak is stocky, broad at the base, making up slightly less than half the length of the skull. In shape, it most closely resembles the beak of some extant suboscines, e.g., the genera Elaenia or Tyrannus, and to a lesser extent, woodpeckers, e.g., the genus Dendrocopos. The oval nostrils are quite long, reaching half the length of the beak. The interorbital width of the frontal bone is relatively narrow; in extant woodpeckers, with the exception of the genus Jynx, it is usually much wider.

Aves indet., specimen A

The specimen MSMD Av JAM2_3a+b (Figure 4) consists of a partial leg preserved on two slabs. The distal femur, the tibiotarsus without the distal part, the tarsometatarsus without the proximal part, and the toes are recognizable. Only the insides of the bones are visible; their surfaces are not preserved, making the precise boundaries between individual bones difficult to determine. The foot has an anisodactyl arrangement of the toes, with three digits pointing forward and one digit pointing backward. The tibiotarsus is bent at the distal end before (not preserved) articulation with the tarsometatarsus, which may be natural or result from a transverse fracture of the shaft. Digit III is the longest, digits II and IV are similar in length, and their phalanges overlap, making it impossible to accurately recognize and measure them. The claws show little curvature, and their tubercula flexoria are poorly developed, which excludes Accipitriformes, Strigiformes and Falconiformes.

Measurements (approximate length, in mm): femur: distal width, 6.5; tibiotarsus (as preserved), 62.7; tarsometatarsus (as preserved), ~33.7; hallux: proximal phalanx, 8.2; hallux: claw, 4.2; digit III (sum of all phalages), ~31.6; first phalanx of digit III, ~8.8; second phalanx of digit III, ~9.2; third phalanx of digit III, ~8.1; claw of digit III, ~5.5.

Aves indet., specimen B

Specimen MSMD Av JAM2_4a+b (Figure 5) consists of the right foot of a small bird preserved on two slabs, seen in lateral view (slab A) and in medial view (slab B). The bone surfaces are not preserved; only the insides are visible. A short and stout tarsometatarsus is observed in Upupiformes, Caprimulgiformes, Coraciiformes, and some Passeriformes, among others. In hummingbirds (Trochilidae), the tarsometatarsus is also short but slender. Among these groups, the total length of the tarsometatarsus (<11 mm) and the overall appearance more closely resemble representatives of the Paleogene genera Laurillardia and Messelirrisor (for measurements and comparisons, see Mayr et al., 2020). The hypotarsus is short proximo-distally and is almost indistinguishable from the shaft because it projects very slightly plantarly, which distinguishes it from most Caprimulgiformes, Coraciiformes, Apodiformes, and Passeriformes, with the exception of, for example, Meliphagidae and Miocene specimens from New Zealand (De Pietri et al., 2024). Trochleae metatarsorum II, III, and IV appear to extend equally far distally and be arranged either in a single plane or slightly deviated from it, which, depending on their actual appearance, would be consistent with Passeriformes, Trochilidae or Upupiformes. Typically for most birds, the foot has an anisodactyl arrangement of the toes, with three digits pointing forward and one digit pointing backward. The proximal phalanx of digit I (hallux) is stout and its length is about one-third that of the tarsometatarsus. The hallux attaches to the tarsometatarsus near the distal end, which differs from the condition in Trochilidae in which the hallux attaches to the distal third of the tarsometatarsus (Louchart et al., 2008; own observations). Phalanges of digits II, III, and IV are close together, which may indicate syndactyly--a feature found especially in Upupiformes and Coraciiformes, but also occasionally in many different bird groups (Botelho et al., 2015). Digit III is the longest, longer even than the tarsometatarsus. The phalanges of digits II and IV overlap, complicating their distinction. All three preserved ungual phalanges (claws) are large, slightly curved, and their tubercula flexoria are poorly developed.

Measurements (maximum length in mm) taken from the main slab (A) or the counterslab (B): tarsometatarsus, 10.6 (A), 10.7 (B); hallux: proximal phalanx, 5.1 (A, B); hallux: claw, 3.2 (A), 3.1 (B); first phalanx of digit III, 2.3 (A), 2.4 (B); second phalanx of digit III, 3.0 (A), 2.8 (B); third phalanx of digit III, 3.2 (A), 3.5 (B); claw of digit III, 3.5 (A, B).

DISCUSSION

The Jamna Dolna site has two outcrops known in the literature under very similar names: Jamna Dolna and Jamna Dolna 2. Including the four specimens currently described, the two outcrops yielded a total of 10 specimens of Oligocene birds. Originally, both outcrops were dated to the Early Oligocene, with the dating of Jamna Dolna 2 being uncertain (Bienkowska-Wasiluk, 2010). Only the discovery of an index taxon, the teleost fish Argyropelecus cosmovici, allowed for a reliable correlation of the fossils from Jamna Dolna 2 with ichthyofaunal zone IPM6, which corresponds to the Late Oligocene (Bienkowska-Wasiluk et al., 2025). This "rejuvenation" of Jamna Dolna 2 has consequences for the dating of three bird specimens and their relation to younger ornithofauna: Ralloidea indet., Carpathiavis meniliticus, and Aviraptor longicrus, described in three subsequent publications by Mayr and Bochenski (2016), Mayr (2019), and Mayr and Hurum (2020), respectively. Here, we are merely signaling a problem that is beyond the scope of this paper.

The preserved skeletal elements of Jamninkaornis kencampbelli (coracoid and humerus) are highly diagnostic. Features such as the hooked processus acrocoracoideus and reduced and rounded processus lateralis (coracoid), and prominent processus flexorius and processus supracoracoideus (humerus) allow for the unambiguous identification of Jamninkaornis kencampbelli as a passerine. Within this group, a highly elongated processus procoracoideus occurs only in some suboscines (Mayr and Manegold, 2006a; Riamon et al., 2020), which places Jamninkaornis kencampbelli within this group. A more detailed identification of Jamninkaornis kencampbelli within suboscines, however, would be too risky. Certain features (e.g., a processus flexorius with a straight dorsal edge) seem to support Tyrannides (see Riamon et al., 2020), but as it later turned out, they also occur in representatives of Eurylaimides, therefore, no clear taxonomic conclusions can be drawn from them (Lowi-Merri et al., 2024).

The slightly larger humerus:coracoid ratio in Jamninkaornis kencampbelli than in other Oligocene passerines and 29 extant Suboscines available in the ISEZ PAN collection (1.3 vs 1.0-1.2, respectively) may result from the relatively longer processus flexorius in the fossil. This difference is so small that it cannot be ruled out that a similar ratio value may occur in other species not studied by us. Therefore, at this stage, it cannot be expected that this is an exclusive feature of Jamninkaornis kencampbelli.

All new passerine taxa from the Paleogene of Europe were found in Early Oligocene (Rupelian) deposits (Mayr, 2022). These include Wieslochia weissi, Jamna szybiaki, Crosnoornis nargizia, Resoviaornis jamrozi, NT-LBR-014, and Winnicavis gorskii, as well as less complete specimens such as wing and leg fragments (Bochenski et al., 2011, 2013, 2014a, 2018, 2021; Mayr and Manegold, 2004, 2006a, 2006b; Riamon et al., 2020). Considerably fewer specimens are dated to the Late Oligocene (Chattian). The only passerine from this period with bones in articulation is a severely damaged foot (Bochenski et al., 2014b); the remaining specimens consist of a few isolated bones (Manegold, 2008; Mourer-Chauvire, 2006). Thus, Jamninkaornis kencampbelli fills this gap to some extent. It provides valuable data closer to the Neogene, helping to fill a gap in our knowledge and potentially documenting the later stages of early passerine evolution. Its scientific value is all the greater because it has associated bones, which may be helpful in future phylogenetic studies.

Most Early Oligocene passerines have a (very) stout humerus if this element is preserved. This was the case in Jamna, Crosnoornis, Resoviaornis, NT-LBR-014 and Winnicavis; judging by the illustrations, Wieslochia is the only exception, having a slender humerus (Bochenski et al., 2011, 2013, 2018, 2021; Mayr and Manegold, 2004, 2006a; Riamon et al., 2020). It thus appears that early passerines differed in the relative stoutness of the humerus. Jamninkaornis kencampbelli already has a thin humerus, almost like in extant passerines. From the Miocene onward, the humerus of passerines is usually slender, although relatively stout humeri still occur in the Miocene (e.g., Happ et al., 2022) and Pliocene (Kessler, 2013).

The lack of diagnostic characters preserved on the skull prevents unambiguous classification of MSMD Av JAM2_2 into a specific taxonomic group. The proposed identification - cf. Suboscines - is tentative and based only on the general similarity in shape and proportions to the Early Oligocene Wieslochia and some extant Suboscines. The shape and size of the beak are correlated with the type of food. MSMD Av JAM2_2 had an unspecialized beak, thus its food - regardless of whether we classify it as Suboscines or not - must have been roughly similar (fruits, insects, and/or seeds) to the food of Wieslochia weissi, Crosnoornis nargizia, and NT-LBR-014 from Luberon, because their beaks are very similar to each other (Mayr and Manegold, 2006a; Bochenski et al., 2021; Riamon et al., 2020; Mayr, 2022). Jamna szybiaki and Resoviaronis jamrozi had more delicate beaks and probably occupied different food niches (Bochenski et al., 2011, 2013). Although the skull (MSMD Av JAM2_2) was found at the same site as Jamninkaornis kencampbelli (MSMD Av JAM2_1a+b) and matches its size, it is unlikely that these specimens belong to the same individual. The surfaces of these two slabs do not show any characteristic features (cracks, ridges, depressions, etc.) that would indicate they were once a single slab.

The partial leg (specimen MSMD Av JAM2_3a+b) is too poorly preserved to even be assigned to an order; we can only exclude groups such as Accipitriformes, Strigiformes, and Falconiformes. The long, thin tibiotarsus and tarsometatarsus resemble those of passerines. However, the broad, rounded bony mass at the distal tarsometatarsus makes it impossible to determine whether the trochleae of the second, third, and fourth digits extend equally far distally and are aligned in a single plane, which is typical for passerines. Its tibiotarsus length was similar to that of the jackdaw Corvus monedula, and the tarsometatarsus length to that of the Siberian jay Perisoreus infaustus, making MSMD Av JAM2_3a+b one of the largest birds from the Polish Oligocene. Only Sobniogallus albinojamrozi and Diomedeoides lipsiensis were comparably large or even larger (Tomek et al., 2014; Elzanowski et al., 2012, respectively), but they differed significantly in appearance from MSMD Av JAM2_3a+b.

To date, 23 specimens of Oligocene birds from 12 sites have been described from the northern part of the Carpathian Arc (Bochenski and Bochenski, 2008; Bochenski et al., 2010, 2011, 2013, 2014a, 2014b, 2016, 2018, 2021, present study; Elzanowski et al., 2012; Gregorová, 2006; Kundrát et al., 2015; Mayr, 2019; Mayr and Bochenski, 2016; Mayr and Gregorová, 2012; Mayr and Hurum, 2020; Mayr et al., 2020; Tomek et al., 2014). Ten sites are located in Poland, and one each in the Czech Republic and Slovakia (Figure 6). These specimens represent a wide variety of taxa, with Passeriformes dominating the identified taxa (eight specimens). Three specimens were assigned to Upupiformes, two to Procellariiformes, and one each to Galliformes, Ralloidea, Apodiformes, Accipitriformes, and Piciformes. The remaining five specimens are birds without established taxonomic affiliations. In total, 13 species have been described from the entire region, including 11 new species. All specimens come from marine sediments, but only two (Procellariformes) are typical marine birds. They were found at the westernmost sites. The remaining birds are terrestrial or semi-aquatic, originating from sites located in the eastern part of the discussed region.

ACKNOWLEDGEMENTS

We are grateful to D. Sobieraj (Poland) for help with processing the photographs.

REFERENCES

AviList Core Team. 2025. AviList: The Global Avian Checklist, v2025.
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