New protocetid whale from the middle eocene of pakistan: birth on land, precocial development, and sexual dimorphism.

<h4>Background</h4>Protocetidae are middle Eocene (49-37 Ma) archaeocete predators ancestral to later whales. They are found in marine sedimentary rocks, but retain four legs and were not yet fully aquatic. Protocetids have been interpreted as amphibious, feeding in the sea but returning...

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Autores principales:	Philip D Gingerich, Munir Ul-Haq, Wighart von Koenigswald, William J Sanders, B Holly Smith, Iyad S Zalmout
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2009
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/bb9cd928fbd24aabb753437cae1f0628
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spelling	oai:doaj.org-article:bb9cd928fbd24aabb753437cae1f06282021-11-25T06:17:31ZNew protocetid whale from the middle eocene of pakistan: birth on land, precocial development, and sexual dimorphism.1932-620310.1371/journal.pone.0004366https://doaj.org/article/bb9cd928fbd24aabb753437cae1f06282009-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/19194487/?tool=EBIhttps://doaj.org/toc/1932-6203<h4>Background</h4>Protocetidae are middle Eocene (49-37 Ma) archaeocete predators ancestral to later whales. They are found in marine sedimentary rocks, but retain four legs and were not yet fully aquatic. Protocetids have been interpreted as amphibious, feeding in the sea but returning to land to rest.<h4>Methodology/principal findings</h4>Two adult skeletons of a new 2.6 meter long protocetid, Maiacetus inuus, are described from the early middle Eocene Habib Rahi Formation of Pakistan. M. inuus differs from contemporary archaic whales in having a fused mandibular symphysis, distinctive astragalus bones in the ankle, and a less hind-limb dominated postcranial skeleton. One adult skeleton is female and bears the skull and partial skeleton of a single large near-term fetus. The fetal skeleton is positioned for head-first delivery, which typifies land mammals but not extant whales, evidence that birth took place on land. The fetal skeleton has permanent first molars well mineralized, which indicates precocial development at birth. Precocial development, with attendant size and mobility, were as critical for survival of a neonate at the land-sea interface in the Eocene as they are today. The second adult skeleton is the most complete known for a protocetid. The vertebral column, preserved in articulation, has 7 cervicals, 13 thoracics, 6 lumbars, 4 sacrals, and 21 caudals. All four limbs are preserved with hands and feet. This adult is 12% larger in linear dimensions than the female skeleton, on average, has canine teeth that are 20% larger, and is interpreted as male. Moderate sexual dimorphism indicates limited male-male competition during breeding, which in turn suggests little aggregation of food or shelter in the environment inhabited by protocetids.<h4>Conclusions/significance</h4>Discovery of a near-term fetus positioned for head-first delivery provides important evidence that early protocetid whales gave birth on land. This is consistent with skeletal morphology enabling Maiacetus to support its weight on land and corroborates previous ideas that protocetids were amphibious. Specimens this complete are virtual 'Rosetta stones' providing insight into functional capabilities and life history of extinct animals that cannot be gained any other way.Philip D GingerichMunir Ul-HaqWighart von KoenigswaldWilliam J SandersB Holly SmithIyad S ZalmoutPublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 4, Iss 2, p e4366 (2009)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Philip D Gingerich Munir Ul-Haq Wighart von Koenigswald William J Sanders B Holly Smith Iyad S Zalmout New protocetid whale from the middle eocene of pakistan: birth on land, precocial development, and sexual dimorphism.
description	<h4>Background</h4>Protocetidae are middle Eocene (49-37 Ma) archaeocete predators ancestral to later whales. They are found in marine sedimentary rocks, but retain four legs and were not yet fully aquatic. Protocetids have been interpreted as amphibious, feeding in the sea but returning to land to rest.<h4>Methodology/principal findings</h4>Two adult skeletons of a new 2.6 meter long protocetid, Maiacetus inuus, are described from the early middle Eocene Habib Rahi Formation of Pakistan. M. inuus differs from contemporary archaic whales in having a fused mandibular symphysis, distinctive astragalus bones in the ankle, and a less hind-limb dominated postcranial skeleton. One adult skeleton is female and bears the skull and partial skeleton of a single large near-term fetus. The fetal skeleton is positioned for head-first delivery, which typifies land mammals but not extant whales, evidence that birth took place on land. The fetal skeleton has permanent first molars well mineralized, which indicates precocial development at birth. Precocial development, with attendant size and mobility, were as critical for survival of a neonate at the land-sea interface in the Eocene as they are today. The second adult skeleton is the most complete known for a protocetid. The vertebral column, preserved in articulation, has 7 cervicals, 13 thoracics, 6 lumbars, 4 sacrals, and 21 caudals. All four limbs are preserved with hands and feet. This adult is 12% larger in linear dimensions than the female skeleton, on average, has canine teeth that are 20% larger, and is interpreted as male. Moderate sexual dimorphism indicates limited male-male competition during breeding, which in turn suggests little aggregation of food or shelter in the environment inhabited by protocetids.<h4>Conclusions/significance</h4>Discovery of a near-term fetus positioned for head-first delivery provides important evidence that early protocetid whales gave birth on land. This is consistent with skeletal morphology enabling Maiacetus to support its weight on land and corroborates previous ideas that protocetids were amphibious. Specimens this complete are virtual 'Rosetta stones' providing insight into functional capabilities and life history of extinct animals that cannot be gained any other way.
format	article
author	Philip D Gingerich Munir Ul-Haq Wighart von Koenigswald William J Sanders B Holly Smith Iyad S Zalmout
author_facet	Philip D Gingerich Munir Ul-Haq Wighart von Koenigswald William J Sanders B Holly Smith Iyad S Zalmout
author_sort	Philip D Gingerich
title	New protocetid whale from the middle eocene of pakistan: birth on land, precocial development, and sexual dimorphism.
title_short	New protocetid whale from the middle eocene of pakistan: birth on land, precocial development, and sexual dimorphism.
title_full	New protocetid whale from the middle eocene of pakistan: birth on land, precocial development, and sexual dimorphism.
title_fullStr	New protocetid whale from the middle eocene of pakistan: birth on land, precocial development, and sexual dimorphism.
title_full_unstemmed	New protocetid whale from the middle eocene of pakistan: birth on land, precocial development, and sexual dimorphism.
title_sort	new protocetid whale from the middle eocene of pakistan: birth on land, precocial development, and sexual dimorphism.
publisher	Public Library of Science (PLoS)
publishDate	2009
url	https://doaj.org/article/bb9cd928fbd24aabb753437cae1f0628
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New protocetid whale from the middle eocene of pakistan: birth on land, precocial development, and sexual dimorphism.

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