Acacia atrox Kodela, Telopea 9(2): 415-419, (2001)
Dense, much branched shrubs to 2 (–4) m tall, spreading by suckering. Branchlets glabrous. Phyllodes sessile, quadrangular to terete, with a yellow nerve at apex of each angle (and a less prominent, often incomplete nerve between each of these), (1.5–) 2–4 (–4.5) cm long, 1–1.2 (–1.3) mm wide, patent to slightly inclined, straight, rigid, galls (with a shape similar to a Hakea fruit) commonly formed within some phyllodes, light green (dry), glabrous, gradually tapered to a sharply pungent point, abruptly broadened or splayed at base; glands small, situated near or up to 3 mm above base, a second gland often present 1/3–2/3 from base. Inflorescences rudimentary 1- or 2-branched racemes with axes to 1 mm long (often appearing simple); peduncles 5–21 mm long, glabrous; heads globular, 17–22–flowered, 5–7 mm diam. (dry), cream–coloured to pale yellow. Flowers 5–merous; calyx cupular, shortly dissected. Pods and seeds not seen.
Known only from the Inverell area, North Western Slopes, N.S.W. Grows in clay soil, on basalt, on the upper slope and crest of a low hill in a partly cleared paddock in eucalypt woodland with grassy ground-cover. There are some concerns that this species could be spreading (by root suckering) and may become a weed hazard within the agricultural system where it occurs. However, until recently it was not appreciated that this represented a seemingly rare new species; it has now been Provisionally Listed as an Endangered Species on the NSW Threatened Species Conservation Act , 1995. Flowers recorded in May and July; pods not seen.
Acacia atrox is a very distinctive species in having quadrangular-terete, pungent, sessile phyllodes that are markedly splayed at their base. Acacia pachypoda from W.A. is the only other Acacia with splayed phyllode bases, however, the two species are not closely related. In the absence of pods it is difficult to determine relationships for this new species. Acacia carneorum and A. pickardii superficially resemble A. atrox in having a gregarious suckering habit, rigid, pungent phyllodes, globular heads and united sepals; however, neither of these species has splayed phyllode bases. Acacia carneorum is further distinguished by its often thicker, distinctly quadrangular phyllodes (with a nerve at the apex of each angle - no intervening nerves present), hairy branchlets and simple inflorescences with yellow to bright yellow heads. Acacia pickardii has erect, terete, obscurely 4–nerved phyllodes, spinose stipules, simple inflorescences and sepals free. The phyllodes of A. colletioides are superficially similar to those in A. atrox , however they are strongly 8–veined, not splayed at their base and are inserted on distinct raised stem projections; also the sepals are free in A. colletioides .
Type of accepted name
New South Wales: North Western Slopes: Inverell area, c. 18 km S of Delungra, W of Inverell, 17 July 2000, W.Hawes, P.O’Keefe & J.Kewley s.n. (NSW445997); holo: NSW; iso: CANB, K, MEL, MO, PERTH.
N.S.W.: Type locality, 25 May 2000, F.Millar (BRI, NSW, PERTH) and T.Tame 6285 (BRI, CANB, MEL, MO, NSW, PERTH).
This species was not included in the Fl. Australia treatment of Acacia. The above account of this new species is based on text provided for use in WATTLE by P.Kodela.