Kumimanu fordycei n. sp.; Petradyptes stonehousei n. gen. n. sp. (1 Viewer)

[Fred Ruhe]

Daniel T. Ksepka, Daniel J. Field, Tracy A. Heath, Walker Patt, Daniel B. Thomas, Simone Giovanardi & Alan J. D., Tennyson, 2023

Largest-known fossil penguin provides insight into the early evolution of sphenisciform body size and flipper anatomy

Journal of Paleontology: 1–20.
doi:10.1017/jpa.2022.88

Abstract: Largest-known fossil penguin provides insight into the early evolution of sphenisciform body size and flipper anatomy | Journal of Paleontology | Cambridge Core

Recent fossil discoveries from New Zealand have revealed a remarkably diverse assemblage of Paleocene stem group penguins. Here, we add to this growing record by describing nine new penguin specimens from the late Paleocene (upper Teurian local stage; 55.5–59.5 Ma) Moeraki Formation of the South Island, New Zealand. The largest specimen is assigned to a new species, Kumimanu fordycei n. sp., which may have been the largest penguin ever to have lived. Allometric regressions based on humerus length and humerus proximal width of extant penguins yield mean estimates of a live body mass in the range of 148.0 kg (95% CI: 132.5 kg–165.3 kg) and 159.7 kg (95% CI: 142.6 kg–178.8 kg), respectively, for Kumimanu fordycei. A second new species, Petradyptes stonehousei n. gen. n. sp., is represented by five specimens and was slightly larger than the extant emperor penguin Aptenodytes forsteri. Two small humeri represent an additional smaller unnamed penguin species. Parsimony and Bayesian phylogenetic analyses recover Kumimanu and Petradyptes crownward of the early Paleocene mainland NZ taxa Waimanu and Muriwaimanu, but stemward of the Chatham Island taxon Kupoupou. These analyses differ, however, in the placement of these two taxa relative to Sequiwaimanu, Crossvallia, and Kaiika. The massive size and placement of Kumimanu fordycei close to the root of the penguin tree provide additional support for a scenario in which penguins reached the upper limit of sphenisciform body size very early in their evolutionary history, while still retaining numerous plesiomorphic features of the flipper.

Enjoy,

Fred

 

[Fred Ruhe]

Systematic paleontology

Aves Linnaeus, 1758
Sphenisciformes Sharpe, 1891
Kumimanu Mayr, Scofield, De Pietri, and Tennyson 2017

Type species.—Kumimanu biceae Mayr, Scofield, De Pietri, and Tennyson 2017.

Revised diagnosis.—Differs from all other Paleocene penguins in larger size and in robust femur shaft (observable only in Kumimanu biceae). Differs from Waimanu, Muriwaimanu Mayr et al., 2017b, Sequiwaimanu Mayr et al., 2017b, and Petradyptes n. gen. in lacking ovoid depressions on the lateral faces of the posterior thoracic vertebrae. Differs from Muriwaimanu, Sequiwaimanu, and Kupoupou in impressio m. pectoralis forming an extremely wide fossa. Differs from Waimanu, Muriwaimanu, Sequiwaimanu, and Crossvallia in greater distal extension of insertion scar for m. supracoracoideus (condition unknown in Waimanu) and placement of sulcus extensorius of tibiotarsus close to midline. Differs from Kaiika and Petradyptes in less strongly flattened humeral shaft. Further differs from all post-Paleocene penguins other than Kaiika in having the border of the sulcus scapulotricipitalis formed by a short posterior trochlear ridge, positioned on the ventral face of the humerus (versus a longer posterior trochlear ridge extending to the caudal border of the humeral shaft in Eocene and later penguins).

Kumimanu fordycei new species

Holotype.—NMNZ S.47426: complete cervical vertebra, partial right coracoid, partial right scapula, nearly complete right humerus, shaft of right ulna, tentatively identified left and right patellae, fragment of left tibiotarsus, and several unidentified fragments of bone.

Diagnosis.—Differs from Kumimanu biceae by substantially larger size (humerus midshaft width 40.7 mm versus 33.0 mm), more curved humerus shaft, and proportionally less expanded proximal end (proximal width ≈ 2.0 times midshaft width versus 2.27 times midshaft width in Kumimanu biceae).

Occurrence.—The holotype was collected in a beach-washed concretion from the Moeraki Formation at Hampden Beach, North Otago, New Zealand. This site is cataloged under NZ Fossil Record Number J42/f0956 (precise locality information is recorded at NMNZ).

Etymology.—In honor of R. Ewan Fordyce, in recognition of his contributions to the field of paleontology including his discovery, collection, and study of penguin fossils in New Zealand and Antarctica, and his generous mentorship of many paleontologists, including authors DTK and DBT, throughout their careers.

Remarks.—Kumimanu fordycei is a candidate for the largest
known penguin.


Figure 1. Kumimanu fordycei n. sp. holotype (NMNZ S.47426). (1) Holotype block oriented to show humerus in dorsal view with humerus of an extant emperor penguin (Aptenodytes forsteri; NMNZ OR.23039) oriented in the same view to indicate scale, (2) block oriented with humerus in ventral view (partially overlain by scapula), (3) comparison of fifth cervical vertebra in caudal view with fifth cervical vertebra of emperor penguin for scale, (4) oblique view of humerus showing wide
fossa formed by impressio m. pectoralis (which is partially hidden by overlying elements) in ventral view. (5) Distal portion of ulna shaft in dorsal view. (6) Close-up of tentatively identified patella. (7) Block oriented with distal end of humerus exposed and (8) close up of distal trochlea. Abbreviations: acr, processus acrocoracoideus; ch, caput humeri; cor, coracoid; cv, cervical vertebral; ft, fossa tricipitalis; hu, humerus; ip, impressio m. pectoralis; mtr, middle trochlear ridge; pat, patella; sb; scapular blade; sup, insertion scar for m. supracoracoideus; tc, tuberculum coracoideum, vtr, ventral trochlear ridge. Scale bars equal 10 mm.

 

[Fred Ruhe]

cf. Kumimanu biceae

Holotype.—NMNZ S.45877: associated partial skeleton including three vertebrae and partial synsacrum, partial left scapula and right coracoid, cranial section of sternum, partial left humerus and ulna, right femur, and partial right tibiotarsus.

Occurrence.—Late Paleocene Moeraki Formation at Hampden Beach, North Otago, New Zealand.

Materials.—NMNZ S.47931: fragments of rib and ilium, proximal end of right femur and shaft of left femur, proximal ends of left tibiotarsus and fibula.

Remarks.—The referred specimen also belongs to a giant penguin, but is too small to belong to Kumimanu fordycei. The proximal end of the right femur is 45 mm wide versus 52 mm in the holotype of Kumimanu biceae, suggesting it may belong to a smaller individual of that species. Intraspecific size variation in stem penguins remains poorly understood, but the referred leg bones provide additional support for recognition of two species of Kumimanu because the holotype specimen of K. fordycei represents an individual ∼15% larger than that represented by the holotype specimen of K. biceae, which in turn represents an individual ∼15% larger than NMNZ S.47931.


Figure 2. cf. Kumimanu biceae (NMNZ S.47931) proximal end of right femur and shaft of left femur, proximal ends of left tibiotarsus and fibula. Abbreviations: cc, crista cnemialis cranialis; cl, crista cnemialis lateralis; fe, femur; fib, fibula, il, tentatively identified iliac blade fragment; rib, rib. Scale bar equals 10 mm.

 

[Fred Ruhe]

Petradyptes stonehousei new species

Holotype.—NMNZ S.47114: nearly complete right humerus
and distal portion of left femur.

Diagnosis.—Differs from all other Paleocene penguins in strongly flattened humerus shaft (midshaft width more than twice midshaft depth). Differs from Muriwaimanu, Sequiwaimanu, and Kupoupou in wider fossa formed by impressio m. pectoralis. Differs from Muriwaimanu, Sequiwaimanu, and Crossvallia in more distally extended insertion scar for m. supracoracoideus. Differs from Kaiika in proportionally wider humerus shaft, greater proximodistal length of crista bicipitalis, and more proximodistally elongate scar for m. supracoracoideus. We note that the deep groove on the tuberculum ventrale of Kaiika maxwelli, which was originally considered autapomorphic for that species, is more likely to be an artifact of incomplete preservation of the natural mold used to cast the holotype humerus.

Occurrence.—Late Paleocene Moeraki Formation, Hampden Beach, North Otago, New Zealand.

Etymology.—In honor of Bernard Stonehouse, in recognition of his landmark contributions to the study of penguins, as well as his work on other New Zealand birds and his generous
encouragement of fossil penguin researchers.

Material.—NMNZ S.46081: partial sternum, associated ribs, left radiale, complete left carpometacarpus, partial synsacrum and right ilium, right femur missing distal end, and proximal ends of right tibiotarsus and fibula. NMNZ S.47146: two thoracic vertebrae, several ribs, partial scapula, partial pelvis, nearly complete left femur. NMNZ S.47927: fragment of synsacrum, multiple ribs, partial scapula, distal end of right carpometacarpus, postacetabular portion of ilium, femoral shaft, distal end of left tibiotarsus. NMNZ S.47933: three cervical and two thoracic vertebrae, five partial ribs, partial left scapula, proximal end of right humerus, proximal end of right tibiotarsus. One fragment of bone appears to represent part of the sternum but is too incomplete to verify.

Remarks.—Fordyce (1991) briefly described a crushed tibiotarsus (OU 8743), which could potentially belong to Petradyptes stonehousei. The width of the distal end of the tibiotarsus is 34.0 mm in OU 8743, which compares well to the width of >30.7 mm (margins partially lost to erosion) in NMNZ S.47927.


Figure 3. Petradyptes stonehousei n. gen. n. sp. holotype (NMNZ S.47114) complete right humerus and distal portion of left femur in (1) ventral viewand (2) dorsal view. Abbreviations: cb, insertion scar for m. coracobrachialis caudalis; cc, insertion scar for m. coracobrachialis caudalis; fe, femur shaft; ft, fossa tricipitalis; ip, impressio m. pectoralis; ftd, fossa tricipitalis dorsalis; sup, insertion scar for m. supracoracoideus. Scale bar equals 10 mm.

 

[Fred Ruhe]

Sphenisciformes indet.

Occurrence.—Late Paleocene Moeraki Formation, Hampden
Beach, North Otago, New Zealand.

Material.—NMNZ S.46080: proximal end of left humerus, one rib, and two unidentified fragments of bone. NMNZ S.47665: right humerus lacking distal end.

Remarks.—These specimens are too incomplete to justify erecting a new taxon. We consider it likely they belong to the same species based on size, but this cannot be confirmed due to their incompleteness. Regardless, these smaller fossils support the presence of a fourth distinct penguin species in the Moeraki Formation.

Fred

 

[Björn Bergenholtz]

Petradyptes stonehousei new species
[...]
Etymology.—In honor of Bernard Stonehouse, in recognition of his landmark contributions to the study of penguins, ...
[...]

The dedicatee ought to be this guy.

 

[Fred Ruhe]

Yes, it seems you are right Björn,

Fred

 

[Fred Ruhe]

I am sorry, but I did forget to give some details on the genus Petradyptes new genus.

Petradyptes new genus

Type species.—Petradyptes stonehousei n. gen. n. sp.

Diagnosis.—As for the type species by monotypy.

Etymology.—From the Greek petra for rock and dyptes for diver. In Ancient Greek, petra carries a connotation of rock cliffs by the sea, eliciting the fossil locality.

Remarks.—Although not the most complete of the specimens, we selected NMNZ S.47114 as the holotype to ease comparisons with existing Paleocene penguin species, the majority of which are based on holotypes that include a humerus. Several additional specimens are also assigned to Petradyptes. NMNZ S.47933 also preserves the proximal end of the humerus, which agrees well in size and morphology with the holotype and preserves the proximal end of the tibiotarsus, which in turn agrees well with the proximal tibiotarsus of NMNZ S.46081. NMNZ S.46081 preserves the femur and carpometacarpus, allowing comparisons to NMNZ S.47146 and NMNZ S.47927. This chain of evidence and the consistent overall size of the specimens support the conclusion that all belong to Petradyptes, although we consider these referrals provisional pending discovery of more complete
specimens preserving the humerus.

I will also give the cladogram of Paleocen Penguins

Fred


Figure 1. Phylogenetic relationships of Paleocene penguins. (1) Strict consensus 7,128 MPTs of 601 steps (CI = 0.628, RI = 0.861, RC = 0.541) from parsimony analysis, with bootstrap support indicated. (2) Maximum sampled-ancestor clade credibility tree summarized from the Bayesian combined-evidence analysis in RevBayes. Posterior probabilities are shown for internal nodes. Sampled ancestors are colored blue and posterior probabilities for the MSACC sampled ancestor positions in this tree are shown in blue. Skeletal reconstructions are provided to show the relative sizes of (3) Kumimanu fordycei n. sp., (4) Petradyptes stonehousei n. gen. n. sp., and (5) the extant emperor penguin Aptenodytes forsteri. Bones preserved in the fossil specimens described in this paper are indicated in white. Skeletal
reconstructions by Simone Giovanardi.