Fred Ruhe
Well-known member
SOCIETY OF VERTEBRATE PALEONTOLOGY OCTOBER 2019
ASBTRACTS OF PAPERS
79TH ANNUAL MEETING
Brisbane Convention and Exhibition Centre
Brisbane, Queensland, Australia
October 9-12, 2019
http://vertpaleo.org/Annual-Meeting...am-book-v5_w-covers.aspx?vsmaid=573&vcid=5063
Bird relates program:
WEDNESDAY AFTERNOON, OCTOBER 9, 2019
TECHNICAL SESSION V: CENOZOIC BIRDS
MEETING ROOM M4
MODERATORS: Thomas Stidham and Anusuya Chinsamy-Turan
A. Chinsamy-Turan, T. H. Worthy, W. D. Handley GROWTH STRATEGIES LINKED TO PREVAILING ENVIRONMENTAL CONDITIONS IN AUSTRALIAN GIANT FLIGHTLESS MIHIRUNG BIRDS (AVES: DROMORNITHIDAE)
The dromornithids were giant flightless birds endemic to Australia. They are
known from the late Paleogene to the late Pleistocene and are represented by eight species in four genera. Here we focus on the largest known dromornithid, and among the heaviest birds (about 610 Kg), the late Miocene aged Dromornis stirtoni; and the medium sized Genyornis newtoni that probably weighed about 250 Kg. Genyornis is the youngest member of the dromornithids and became extinct about 40 000 years ago. Since little is known about the biology of these birds, we undertook a histological investigation of their bones to deduce various aspects of their life history. This study focuses on four tibiotarsi, two tarsometatarsi and a femur of Genyornis that were recovered from the northern desert regions of South Australia. In addition, we expanded our previous osteohistology sample by including additional younger and adult specimens of Dromornis from the late Miocene Alcoota Local Fauna in the Northern Territory of Australia. The bone histology of Dromornis and Genyornis show that these birds experienced a cyclical pattern of growth with alternating rapid and slower rates of osteogenesis. During faster periods of growth they deposited fibrolamellar bone tissue, whilst during periods of slowed growth they formed lamellar bone tissue, which was sometimes associated with lines of arrested growth indicating pauses in osteogenesis and growth. However, we found that these birds differed in the amount of time taken to grow to maturity: Dromornis has over 10 growth cycles while Genyornis shows a maximum of 3 growth cycles. Interestingly, in Genyornis some of the lamellar deposits are wide, indicating that they grew slowly for longer periods of time. The main aridification of Australia is considered to have occurred from the Late Miocene through to the Pleistocene. We postulate that the growth dynamics of the dromornithids were adapted to the particular environment in which they lived, i.e., Dromornis lived before the main aridification and therefore a k-selected lifestyle strategy would have been advantageous. However, as landscape resources became less predictable, then r-selected strategies were favoured by Genyornis. The wide bands of lamellar bone in some of the Genyornis samples may be coincident with lengthy stressful periods (drought).
ASBTRACTS OF PAPERS
79TH ANNUAL MEETING
Brisbane Convention and Exhibition Centre
Brisbane, Queensland, Australia
October 9-12, 2019
http://vertpaleo.org/Annual-Meeting...am-book-v5_w-covers.aspx?vsmaid=573&vcid=5063
Bird relates program:
WEDNESDAY AFTERNOON, OCTOBER 9, 2019
TECHNICAL SESSION V: CENOZOIC BIRDS
MEETING ROOM M4
MODERATORS: Thomas Stidham and Anusuya Chinsamy-Turan
A. Chinsamy-Turan, T. H. Worthy, W. D. Handley GROWTH STRATEGIES LINKED TO PREVAILING ENVIRONMENTAL CONDITIONS IN AUSTRALIAN GIANT FLIGHTLESS MIHIRUNG BIRDS (AVES: DROMORNITHIDAE)
The dromornithids were giant flightless birds endemic to Australia. They are
known from the late Paleogene to the late Pleistocene and are represented by eight species in four genera. Here we focus on the largest known dromornithid, and among the heaviest birds (about 610 Kg), the late Miocene aged Dromornis stirtoni; and the medium sized Genyornis newtoni that probably weighed about 250 Kg. Genyornis is the youngest member of the dromornithids and became extinct about 40 000 years ago. Since little is known about the biology of these birds, we undertook a histological investigation of their bones to deduce various aspects of their life history. This study focuses on four tibiotarsi, two tarsometatarsi and a femur of Genyornis that were recovered from the northern desert regions of South Australia. In addition, we expanded our previous osteohistology sample by including additional younger and adult specimens of Dromornis from the late Miocene Alcoota Local Fauna in the Northern Territory of Australia. The bone histology of Dromornis and Genyornis show that these birds experienced a cyclical pattern of growth with alternating rapid and slower rates of osteogenesis. During faster periods of growth they deposited fibrolamellar bone tissue, whilst during periods of slowed growth they formed lamellar bone tissue, which was sometimes associated with lines of arrested growth indicating pauses in osteogenesis and growth. However, we found that these birds differed in the amount of time taken to grow to maturity: Dromornis has over 10 growth cycles while Genyornis shows a maximum of 3 growth cycles. Interestingly, in Genyornis some of the lamellar deposits are wide, indicating that they grew slowly for longer periods of time. The main aridification of Australia is considered to have occurred from the Late Miocene through to the Pleistocene. We postulate that the growth dynamics of the dromornithids were adapted to the particular environment in which they lived, i.e., Dromornis lived before the main aridification and therefore a k-selected lifestyle strategy would have been advantageous. However, as landscape resources became less predictable, then r-selected strategies were favoured by Genyornis. The wide bands of lamellar bone in some of the Genyornis samples may be coincident with lengthy stressful periods (drought).
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