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Osteology Supports a Stem-Galliform Affinity for the Giant Extinct Flightless Bird Sylviornis neocaledoniae (Sylviornithidae, Galloanseres).

Worthy TH, Mitri M, Handley WD, Lee MS, Anderson A, Sand C - PLoS ONE (2016)

Bottom Line: Sylviornis neocaledoniae is found to be a stem galliform, distant from megapodiids, and the sister taxon to the extinct flightless Megavitiornis altirostris from Fiji, which we transfer to the family Sylviornithidae.These observations and its phylogenetic placement as stem galliforms makes it improbable that this species employed ectothermic incubation or was a mound-builder.Sylviornis neocaledoniae can therefore be excluded as the constructor of tumuli in New Caledonia.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, Flinders University, Adelaide, South Australia, Australia.

ABSTRACT
The giant flightless bird Sylviornis neocaledoniae (Aves: Sylviornithidae) existed on La Grande Terre and Ile des Pins, New Caledonia, until the late Holocene when it went extinct shortly after human arrival on these islands. The species was generally considered to be a megapode (Megapodiidae) until the family Sylviornithidae was erected for it in 2005 to reflect multiple cranial autapomorphies. However, despite thousands of bones having been reported for this unique and enigmatic taxon, the postcranial anatomy has remained largely unknown. We rectify this deficiency and describe the postcranial skeleton of S. neocaledoniae based on ~600 fossils and use data from this and its cranial anatomy to make a comprehensive assessment of its phylogenetic affinities. Sylviornis neocaledoniae is found to be a stem galliform, distant from megapodiids, and the sister taxon to the extinct flightless Megavitiornis altirostris from Fiji, which we transfer to the family Sylviornithidae. These two species form the sister group to extant crown-group galliforms. Several other fossil galloanseres also included in the phylogenetic analysis reveal novel hypotheses of their relationships as follows: Dromornis planei (Dromornithidae) is recovered as a stem galliform rather than a stem anseriform; Presbyornis pervetus (Presbyornithidae) is the sister group to Anseranatidae, not to Anatidae; Vegavis iaai is a crown anseriform but remains unresolved relative to Presbyornis pervetus, Anseranatidae and Anatidae. Sylviornis neocaledoniae was reconstructed herein to be 0.8 m tall in a resting stance and weigh 27-34 kg. The postcranial anatomy of S. neocaledoniae shows no indication of the specialised adaptation to digging seen in megapodiids, with for example, its ungual morphology differing little from that of chicken Gallus gallus. These observations and its phylogenetic placement as stem galliforms makes it improbable that this species employed ectothermic incubation or was a mound-builder. Sylviornis neocaledoniae can therefore be excluded as the constructor of tumuli in New Caledonia.

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PCA plot showing separation of S. neocaledoniae from various megapodes and Gallus gallus.The plot is based on leg bone measurements standardised for size using femur length and selected ratios of some lengths divided by tarsometatarsus length of various galliforms compared to (see S1 File).
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pone.0150871.g012: PCA plot showing separation of S. neocaledoniae from various megapodes and Gallus gallus.The plot is based on leg bone measurements standardised for size using femur length and selected ratios of some lengths divided by tarsometatarsus length of various galliforms compared to (see S1 File).

Mentions: The datasets for measurements of femora, tibiotarsi, tarsometatarsi and phalanges (S1 File) were visualised with Principal Component Analyses conducted in PAST v3.08 [35]. Individuals for species formed discrete clusters and species were clearly segregated on the PC1 and PC2 axes by trends in two main planes (Fig 12). PC1 accounted for the majority of discrimination, determined by the Scree plot and a Loadings plot (see S4 File) with just seven variables driving the separation of the taxa in the PCA (phal I.1L/femL, phal I.2L/femL, phal III.4L/femL, phal I.1L/tmtL, phal I.2L/tmtL, phal III.4L/tmtL, phal 3.4SW/SD). A biplot of variables showed that tmtL/femL was an additional a major driver on the PC2 axis (confirmed in a Loadings plot of PC2). The broad confidence interval for tmtL/FemL on loadings plot probably relates to the fact that much of the separation relates to the single point for Sylviornis neocaledoniae relative to the remaining individuals. Thus in Fig 12, birds with relatively short tarsometatarsi lie more negative on the PC2 axis, so separating for example, Macrocephalon maleo from Leipoa ocellata. Simultaneously, relative length of the proximal phalanges to femur length separated birds with more elongate phalanges to the upper right on the plot from birds with relatively shorter phalanges towards the lower left. Because of the non-correlation of tarsometatarsus length and femoral length, birds with elongate proximal phalanges relative to tarsometatarsi grouped to the lower right, thus separating S. neocaledoniae and L. ocellata from G. gallus. Lastly, the degree of dorsoventral flattening of ungual phalanx III.4, a proxy for all anterior unguals, is a major driver of separation on the PC1 axis. Taxa that are well known for great dorsoventral compression, e.g. the Megapodius species, are well separated to the right, with Gallus gallus the farthest left on PC1. Thus, S. neocaledoniae, which is well separated in the lower left of the PCA, has relative to femur length the shortest tarsometatarsus and the shortest proximal phalanges of compared taxa, and an ungual phalanx III.4 that is slightly deeper than wide at mid-length. Its ungual compression is similar to M. maleo and Talegalla fuscirostris, but not so enhanced as in G. gallus. In summary, S. neocaledoniae lies outside of all other megapodes, in the same direction as does G. gallus, and the best mound builders are the most distant.


Osteology Supports a Stem-Galliform Affinity for the Giant Extinct Flightless Bird Sylviornis neocaledoniae (Sylviornithidae, Galloanseres).

Worthy TH, Mitri M, Handley WD, Lee MS, Anderson A, Sand C - PLoS ONE (2016)

PCA plot showing separation of S. neocaledoniae from various megapodes and Gallus gallus.The plot is based on leg bone measurements standardised for size using femur length and selected ratios of some lengths divided by tarsometatarsus length of various galliforms compared to (see S1 File).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4814122&req=5

pone.0150871.g012: PCA plot showing separation of S. neocaledoniae from various megapodes and Gallus gallus.The plot is based on leg bone measurements standardised for size using femur length and selected ratios of some lengths divided by tarsometatarsus length of various galliforms compared to (see S1 File).
Mentions: The datasets for measurements of femora, tibiotarsi, tarsometatarsi and phalanges (S1 File) were visualised with Principal Component Analyses conducted in PAST v3.08 [35]. Individuals for species formed discrete clusters and species were clearly segregated on the PC1 and PC2 axes by trends in two main planes (Fig 12). PC1 accounted for the majority of discrimination, determined by the Scree plot and a Loadings plot (see S4 File) with just seven variables driving the separation of the taxa in the PCA (phal I.1L/femL, phal I.2L/femL, phal III.4L/femL, phal I.1L/tmtL, phal I.2L/tmtL, phal III.4L/tmtL, phal 3.4SW/SD). A biplot of variables showed that tmtL/femL was an additional a major driver on the PC2 axis (confirmed in a Loadings plot of PC2). The broad confidence interval for tmtL/FemL on loadings plot probably relates to the fact that much of the separation relates to the single point for Sylviornis neocaledoniae relative to the remaining individuals. Thus in Fig 12, birds with relatively short tarsometatarsi lie more negative on the PC2 axis, so separating for example, Macrocephalon maleo from Leipoa ocellata. Simultaneously, relative length of the proximal phalanges to femur length separated birds with more elongate phalanges to the upper right on the plot from birds with relatively shorter phalanges towards the lower left. Because of the non-correlation of tarsometatarsus length and femoral length, birds with elongate proximal phalanges relative to tarsometatarsi grouped to the lower right, thus separating S. neocaledoniae and L. ocellata from G. gallus. Lastly, the degree of dorsoventral flattening of ungual phalanx III.4, a proxy for all anterior unguals, is a major driver of separation on the PC1 axis. Taxa that are well known for great dorsoventral compression, e.g. the Megapodius species, are well separated to the right, with Gallus gallus the farthest left on PC1. Thus, S. neocaledoniae, which is well separated in the lower left of the PCA, has relative to femur length the shortest tarsometatarsus and the shortest proximal phalanges of compared taxa, and an ungual phalanx III.4 that is slightly deeper than wide at mid-length. Its ungual compression is similar to M. maleo and Talegalla fuscirostris, but not so enhanced as in G. gallus. In summary, S. neocaledoniae lies outside of all other megapodes, in the same direction as does G. gallus, and the best mound builders are the most distant.

Bottom Line: Sylviornis neocaledoniae is found to be a stem galliform, distant from megapodiids, and the sister taxon to the extinct flightless Megavitiornis altirostris from Fiji, which we transfer to the family Sylviornithidae.These observations and its phylogenetic placement as stem galliforms makes it improbable that this species employed ectothermic incubation or was a mound-builder.Sylviornis neocaledoniae can therefore be excluded as the constructor of tumuli in New Caledonia.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, Flinders University, Adelaide, South Australia, Australia.

ABSTRACT
The giant flightless bird Sylviornis neocaledoniae (Aves: Sylviornithidae) existed on La Grande Terre and Ile des Pins, New Caledonia, until the late Holocene when it went extinct shortly after human arrival on these islands. The species was generally considered to be a megapode (Megapodiidae) until the family Sylviornithidae was erected for it in 2005 to reflect multiple cranial autapomorphies. However, despite thousands of bones having been reported for this unique and enigmatic taxon, the postcranial anatomy has remained largely unknown. We rectify this deficiency and describe the postcranial skeleton of S. neocaledoniae based on ~600 fossils and use data from this and its cranial anatomy to make a comprehensive assessment of its phylogenetic affinities. Sylviornis neocaledoniae is found to be a stem galliform, distant from megapodiids, and the sister taxon to the extinct flightless Megavitiornis altirostris from Fiji, which we transfer to the family Sylviornithidae. These two species form the sister group to extant crown-group galliforms. Several other fossil galloanseres also included in the phylogenetic analysis reveal novel hypotheses of their relationships as follows: Dromornis planei (Dromornithidae) is recovered as a stem galliform rather than a stem anseriform; Presbyornis pervetus (Presbyornithidae) is the sister group to Anseranatidae, not to Anatidae; Vegavis iaai is a crown anseriform but remains unresolved relative to Presbyornis pervetus, Anseranatidae and Anatidae. Sylviornis neocaledoniae was reconstructed herein to be 0.8 m tall in a resting stance and weigh 27-34 kg. The postcranial anatomy of S. neocaledoniae shows no indication of the specialised adaptation to digging seen in megapodiids, with for example, its ungual morphology differing little from that of chicken Gallus gallus. These observations and its phylogenetic placement as stem galliforms makes it improbable that this species employed ectothermic incubation or was a mound-builder. Sylviornis neocaledoniae can therefore be excluded as the constructor of tumuli in New Caledonia.

Show MeSH
Related in: MedlinePlus