Taxonomy and Phylogeny
The golden-crowned or Tattersall's sifaka (Propithecus tattersalli), known locally as ankomba malandy (or akomba malandy, meaning "white lemur"), was scientifically discovered in 1974 north of Vohemar in northeast Madagascar by Ian Tattersall, who observed but did not capture the animal. Unsure of its classification, Tattersall provisionally considered it a variant of the silky sifaka in his 1982 book, The Primates of Madagascar, citing its mostly white fur, but also noting its uncharacteristic orange crown patch and tufted ears. Driven by a report in 1986 that the forest where Tattersall had observed this unique sifaka was contracted to be clear-cut for charcoal production, a research team from the Duke Lemur Center, led by Elwyn Simons, obtained permits to capture specimens for a captive breeding program. Simons and his team were the first to capture and observe the golden-crowned sifaka, formally describing it as a new species in 1988 and naming it in honor of Tattersall. The specimens were found 6 to 7 km (3.7 to 4.3 mi) northeast of Daraina, a village in the northeast corner of Madagascar.
There have been conflicting studies regarding the taxonomic status of the golden-crowned sifaka. When described by Simons in 1988, size, vocalizations, and karyotypes (the number and appearance of chromosomes) were compared with the other sifakas. In terms of size, general morphology, and vocalizations, the golden-crowned sifaka is more comparable to the western forest sifakas (known as the P. verreauxi group) in that it is smaller in length and weight. Its karyotype, however, is more similar to that of the eastern forest sifakas (known as the P. diadema group). The golden-crowned sifaka has 42 chromosomes (2n=42), 16 of which are autosomal pairs (not sex chromosomes) that are meta- or submetacentric (where chromosome arms are equal or unequal in length, respectively). The remaining autosomal pairs are smaller and acrocentric (with the shorter chromosome arm difficult to observe). Its X chromosome is metacentric, which is comparable to that of the P. diadema group, not the P. verreauxi group. Given the conflicting information, its geographic isolation, as well as the unique long fur tufts on the ears—a trait not shared by any other sifaka—the golden-crowned sifaka was recognized as a distinct species.
In 1997, comparisons of repeated DNA sequences within the family Indriidae supported Simon's classification, placing the golden-crowned sifaka as a sister group to the other sifakas. In 2001, a study involving mitochondrial DNA suggested a very recent divergence between it and the Coquerel's sifaka, then considered a subspecies of the P. verreauxi group. If this were true, the golden-crowned sifaka would not merit species status and would form a subclade with the Coquerel's sifaka within the P. verreauxi group. In 2004, a comparative study of the karyotypes of the three traditional species of sifakas provided insight into the chromosomal arrangements of all three groups. This study found that the golden-crowned sifaka differs from P. verreauxi group and P. diadema group by 9 and 17 chromosomal rearrangements respectively, and conversely argued that the golden-crowned sifaka is indeed a separate species and is more closely related to the P. verreauxi group. More recently, in 2007 a craniodental (skull and tooth) study provided evidence for 9 or 10 distinct sifaka species, including the golden-crowned sifaka. It also placed the golden-crowned sifaka within the P. verreauxi group.
Read more about this topic: Golden-crowned Sifaka