Eryops megacephalus

ERYOPS MEGACEPHALUS

Eryops megacephalus Cope 1877 is an early tetrapod from the Permian (298.9-251.9 Ma), apparently showing strong similarities to salamanders (2022HerbstEC_HutchinsonJR; 2023CohenKM_CarN). Adults reached an advanced degree of terrestrial habitation and a size of about three meters from head to tail (2002SchochRR).

Eryops megacephalus (Lower Permian); top – reconstruction of the skeleton; bottom – appearance of the animal, sculptor Ya.M. Eglon; exposition of the Orlov Paleontological Museum (Moscow); photo by the author.

Anatomical evidences of the ligamentum capitis femoris (LCF) in Eryops megacephalus is suggested by certain features in fossilized pelvic and femoral bones. Notable LCF indicators on the femur include the fovea capitis, the groove on the femoral head, and the femoral head’s tuberosity. In the pelvic bone, signs of LCF presence include acetabular notches, an acetabular fossa, perforations, and irregularities on the acetabular surface. We used these features to identify LCF in the first amphibians and land species.

According to E.D. Cope (1880) the pelvic bones of Eryops megacephalus resemble «… in their compression below, the corresponding parts in the Anura. The ilia are, however, shorter and worn as in the Urodela. They are flat, and stand at right angles to the line of the ischiopubic symphysis. There is an open concavity of their inferior posterior free border, and a facet-bearing elevation on the inferior border, or that entering into the formation of the acetabulum. The latter is large and half as long again as deep. The anterior and posterior borders of the pelvis descend regularly to the inferior edge, forming with it a triangle. The ischiadic or posterior border is but little thickened; the anterior, or pubic is flat in front and presents a reverted edge outwards. This expands prominently where it is joined by a ridge which bounds the acetabulum below; it there contracts to an inferior apex. Beneath the anterior point of the acetabulum it is pierced by the usual foramen, which issues on the inner edge of the anterior face, just above the symphysis.» (1880CopeED).

Pelvis of Eryops megacephalus; lower center – lateral view, cranial end on the left (1880CopeED, no changed).

A.S. Romer (1922) described the pelvis of early tetrapods as follows: «A constant feature is the presence of a prominent wedge above the acetabulum, merging gradually into the general surface of the bone anteriorly, but posteriorly dropping back sharply as a distinct supra-acetabular notch. This is found practically the same in almost every form examined, from Eryops to the highest therapsids. As suggested by Broili, who first noticed it in dicynodonts (1908, p. 3), it indicates the position of a ligament similar to that found in the cotyloid notch of the ischium of mammals; the changed position of the mammalian femur would account for a shifting ventrally of the notch.»

Right pelvic bone of Eryops megacephalus, lateral view, cranial end on the right; legend: SAN – supra-acetabular notch, TRL – transverse line, F. OBT – obturator foramen, attachment zones of the ilio-ischiadic ligament – lig. il-isch, ilio-puboiliac ligament – lig. il-pub (1922RomerAS, no changed).

Common morphological features between Eryops megacephalus and modern salamanders include a shallow acetabulum (2022HerbstEC_HutchinsonJR). A large notch is clearly visible in the posterosuperior region of the acetabulum.

Pelvis of Eryops megacephalus, modified from Pawley & Warren (Pawley and Warren 2006); illustration from 2018AhlbergPE, no changed).

The acetabular notch is designed to accommodate and attach the LCF. Although the precise positioning of the LCF remains unknown, it is hypothesized to have functioned as a flexible support element activated during terrestrial movement. It is most plausible that the proximal end of the LCF was attached within the supra-acetabular notch, resembling the attachment observed in one of the paired femoral head ligaments in salamanders (1934FrancisETB). The distal end of the LCF in Eryops megacephalus might have attached to the upper edge of the femoral head. In this configuration, LCF tension would restrict medial pelvic tilt during walking, reducing the load on abductor muscles. From our perspective, the LCF in Eryops megacephalus likely did not facilitate pelvic rotation within the horizontal plane.

View of the bones forming the hip joint of Eryops megacephalus, we have marked the supposed localization of LCF; exposition of the Orlov Paleontological Museum (Moscow); photo by the author.

References

Herbst EC, Manafzadeh AR, Hutchinson JR. Multi-joint analysis of pose viability supports the possibility of salamander-like hindlimb configurations in the Permian tetrapod Eryops megacephalus. Integrative and Comparative Biology. 2022;62(2)139-151. [academic.oup.com]

Cohen KM, Harper DAT, Gibbard PL, Car N. The International Commission on Stratigraphy (ICS) International Chronostratigraphic Chart. September 2023. [stratigraphy.org]

Schoch RR. The evolution of metamorphosis in temnospondyls. Lethaia. 2002;35(4)309-27. [idunn.no]

Cope ED. Second Contribution to the History of the Vertebrata of the Permian Formation of Texas. Proceedings of the American Philosophical Society. 1880;19(107)38-58. [jstor.org]

Romer AS. The locomotor apparatus of certain primitive and mammal-like reptiles. Bulletin of the AMNH. 1922;46, art.10:517-647. [digitallibrary.amnh.org]

Broili F. Ein Dicynodonttierreste ausderKarooformation. Neuen Jahrb. Fur Min., Geol., und Paliiont. 1908, I:1-15, P1. I.

Ahlberg PE. Follow the footprints and mind the gaps: a new look at the origin of tetrapods. Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 2018;109(1-2)115-37. [cambridge.org]

Francis ETB. The anatomy of the salamander. Oxford: The Clarendon Press, 1934. [archive.org]

Keywords

ligamentum capitis femoris, ligamentum teres, ligament of head of femur, doctrine, animals, amphibian

The original text in Russian is available at the link: Eryops megacephalus

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BLOG CONTENT

500–1 Mya

Comments

1802PalmeraniÁ

Palmerani Á , drawing Jacob wrestling with the angel (1802 ). Depicting the circumstances and mechanism of the ligamentum capitis femoris (LCF) injury based on the description in the Book of Genesis: 25 And Ja cob was left alone; and there wrestled a man with him until the breaking of the day. 26 And when he saw that he could not prevail against him, he struck against the hollow of his thigh ; and the hollow of Jacob's thigh was put out of joint, as he was wrestling with him. … 33 Therefore do the children of Israel not eat the sinew which shrank, which is upon the hollow of the thigh, unto this day; because he struck against the hollow of Jacob's thigh on the sinew that shrank. ( 1922LeeserI , Genesis (Bereshit) 32:25-26,33) More about the plot in our work: Ninth month, eleventh day ( 2024 АрхиповСВ. Девятый месяц, одиннадцатый день ). Ángel Palmerani – Jacob Wrestling with the Angel ( 1802); original in the a...

Human LCF intersection

HUMAN LCF INTERSECTION In the south of China, in the Guangxi Zhuang Autonomous Region, the archaeological Neolithic site of Dingsishan was investigated. Burials of 355 people were found in this place. The authors of the article (2024YeZ_LiFJ) identified 91 skeletons with traces of manipulations with the remains. They are attributed to burials of the Dingsishan III-IV phase, aged 8.0-4.5 thousand years. 13 notches were found on the proximal part of various femurs. « Cutmarks on the femoral head, neck and intertrochanteric line, as well as along the medial linea aspera of the femoral shaft, suggest that soft tissue around the hip, including the iliofemoral ligament and the iliacus and adductor muscles, was severed to disarticulate the joint.» This and other postmortem bone injuries «... suggests that corpse treatment at Dingsishan included disarticulation » (2024YeZ_LiFJ). Figure 4 of the cited article shows the distribution and direction of cutmarks on human skeletons from Dingx...

1614PagniniS

Content [i] Annotation [ii] Original text (in Latin) [iii] English translation [iv] Source & links [v] Notes [vi] Authors & Affiliations [vii] Keywords [i] Annotation Fragment from the book: Pagnini S. Thesaurus linguae sanctae, sive lexicon hebraicum (1614, Vol. 1). The author examines the translation into Latin of the term denoting ligamentum capitis femoris (LCF) in Hebrew biblical texts. The text in Russian is available at the following link: 1614PagniniS . [ii] Original text (in Latin) Quote, p. 392 ניר est Neruus Genesis 32.32 Idcirco non comedent (pro, comedunt) filij Israel ניר את neruum. Et Iesah 48.4 וניד & nerruus serreus ceruix tua: vel, secundum Rab. Dair. & virga ferrea: sic appellate, quòd nerui sint ceruice בניד in neruo Genes. 32.32. Iech 37.6. Et dabo super vos צירים neruos. Ijob 10. II ossibusq;...

1140St.Marie-Madeleine

Basilica of Saint Mary Magdalene of Vézelay, capital s – Jacob with the Angel (1125 – 1140). Depicting the circumstances and mechanism of the ligamentum capitis femoris (LCF) injury based on the description in the Book of Genesis: 25 And Ja cob was left alone; and there wrestled a man with him until the breaking of the day. 26 And when he saw that he could not pre vail against him, he struck against the hollow of his thigh ; and the hollow of Jacob's thigh was put out of joint, as he was wrestling with him. … 33 Therefore do the children of Israel not eat the sinew which shrank, which is upon the hollow of the thigh, unto this day; because he struck against the hollow of Jacob's thigh on the sinew that shrank. ( 1922LeeserI , Genesis (Bereshit) 32:25-26,33) More about the plot in our work: Ninth month, eleventh day ( 2024 АрхиповСВ. Девятый месяц, одиннадцатый день ). Basilica of Saint Mary Magdalene of Vézelay (1125 – 1140). Capital (...

2003IvanovYV

Ivanov YV, panel, wood carving – Jacob Wrestling with the Angel (2003). Variant of depicting the circumstances and mechanism of the ligamentum capitis femoris (LCF) injury based on the description in the Book of Genesis: 25 And Ja cob was left alone; and there wrestled a man with him until the breaking of the day. 26 And when he saw that he could not pre vail against him, he struck against the hollow of his thigh ; and the hollow of Jacob's thigh was put out of joint, as he was wrestling with him. … 33 Therefore do the children of Israel not eat the sinew which shrank, which is upon the hollow of the thigh, unto this day; because he struck against the hollow of Jacob's thigh on the sinew that shrank. ( 1922LeeserI , Genesis (Bereshit) 32:25-26,33) More about the plot in our work: Ninth month, eleventh day ( 2024 АрхиповСВ. Девятый месяц, одиннадцатый день ). Ivanov Yuri Vitalievich – Jacob Wrestling with the Angel (2003); im...

The First Scientific Mention

European science has known the LCF for about 2500 years. It is the most important functional connection of the hip joint. The first person to describe the LCF was Hippocrates (c. 460-370 BCE). A written mention of the LCF is found in §1 of his treatise "On the Instrument of redactions". In our opinion, a book created in the library of the Asclepeion of the island of Kos. Hippocrates did not dissection of the human body, did not operate on the hip joint, did not have a CT scan and MRI. How he could discover the LCF? In our view, it is possible that Hippocrates treated a patient with an open hip dislocation. Track Music: Blue Dot Sessions , Vittoro (CC BY-NC 4.0 DEED / fragment) keywords: ligamentum capitis femoris, ligament of head of femur, ligamentum teres, hip dislocation . ...

80-58bcApollonius Citiensis

Fragment from the treatise Apollonius Citiensis Commentary on the Hippocrates’ book On Joints ( Περὶ αρθρων π ραγματεὶα , 80-58 BC). The author notes the possibility of damage to the ligamentum capitis femoris (LCF) during hip dislocation. See our commentary at the link: 80-58bcApollonius Citiensis [Rus], and 2020ArkhipovSV_ProlyginaIV . Quote. [Grc] Περὶ αρθρων π ραγματεὶα . Βιβλιον γ ʹ . (original source: 1965KolleschJ_KudlienF, pp. 86, 88) Translation [Eng] Commentary On Joints ( Commentary on the Hippocrates’ book On Joints). Book 3. If the dislocated and displaced hip could not remain in place, then the physician [Hippocrates] would have clearly indicated the incurability of this case, so that we would not be led astray. Don't those who hold the opposite opinion know about the nature of joints, ligaments and the teachings about these things in general? After all, the physician considered the cause of the mild or, on the contrary, complex displacement and ...

1899ParsonsFG

An excerpt from the article by Parsons FG. The joints of mammals compared with those of man: a course of lectures delivered at the Royal College of Surgeons of England (1899, pp. 301-306). The paper discusses the anatomy and presence of the ligamentum capitis femoris (LCF) in different animals. The author found in an experiment that in kangaroos, the LCF was stretched during hip extension. Below we publish an excerpt from the abstract and a critique of the lecture in the Lancet. THEJOINTS OF MAMMALS COMPARED WITH THOSE OF MAN: A COUBSE OF LECTURES DELIVERED AT THE ROYAL COLLEGE OF SURGEONS OF ENGLAND. By F. G. PARSONS, F.R.C.S., late Hunterian Professor. PART II.-JOINTS OF THE HIND LIMB. THE HIP JOINT. SOME of the chief points which attract attention in the hip joint of man are the three thickened parts of the capsule called the ilio-femoral, ischio-femoral, and pubo-femoral ligaments, as well as the intra-articular ligamentum teres running from the bottom of the ac...

Homo antecessor. Hip disarticulation

HOMO ANTECESSOR. Hip disarticulation Postmortem separation of the leg from the pelvis in individuals of own species was performed by our evolutionary predecessors. In particular, this was done in the Homo antecessor community, which practiced cannibalism (2003TuttC). Ferna Y. et al. (1999) described evidence of intentional crushing of the femur diaphysis in a young individual (ATD6-76), presumably to extract bone marrow. The bone retained traces of not only several impacts by a striker, but also of an anvil on which the bone lay. The age of the said find in the Gran Dolina cave (Spain) is estimated at about 780 thousand years (1999FernaY_RosellJ). The above features indicate that the femur was initially separated from the soft tissues. In the second stage, the butcher had to use a stone tool to cut the muscles and strong external ligaments of the hip joint. In the next stage, he tore, or perhaps cut off, the ligamentum capitis femoris (LCF) to mobilize the hip and further manipul...

Vertebrates

VERTEBRATES According to the molecular clock, a specific method for dating phylogenetic events, vertebrates (Vertebrata) separated from arthropods (Arthropoda) 976±97 Ma (2004HedgesSB_ShoeJL). The latter began to dominate in species diversity with the Cambrian burst of radiation, which occurred 520 Ma (2010EdgecombeGD). This ratio in the fauna of the Earth is still preserved. Approximately 525 Ma, the phylum Chordates separated from the group of bilaterally symmetrical animals (1995ChenJY_ZhouGQ). In turn, the evolution of chordate organisms led to the formation of the first vertebrates at least 500 Ma, from which the jawed mouths 450-400 Ma descended, becoming the ancestors of the placoderms or "armored" fish (Placodermi) (1979 НаумовНП _ КарташевНН ). Sculptural reconstruction of the placoderm Coccosteus from the order Arthrodires, Middle Devonian, 393.3-382.7 Ma ; exposition of the Orlov Paleontological Museum (Moscow); photo by the author. The first cartilaginou...

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