Crataegus shandongensis F. Z. Li & W. D. Peng

Crataegus shandongensis F. Z. Li & W. D. Peng, Bull. Bot. Res., Harbin 6: 149. 1986. Type. China. Shandong, Taian, Taishan, alt. 700–800 m, 15 May 1984, W. D. Peng 84001 (lectotype, designated here: PE [barcode 01153319!, Fig. 4 C]; isolectotypes: SDAU!, Fig. 5 A – C). Description. Shrubs 1–2 m tall, thorns 1–1.2 cm long or absent; branchlets initially pubescent and then glabrous, older branches gray-brown, sparsely lenticellate, glabrous. Stipules herbaceous, falcate, margin glandular-serrate. Leaves simple, deciduous; petioles 1.5–4 cm long, narrowly winged, glabrous; blades 4–8 cm long, 2–4 cm wide, obovate or long-elliptic; base cuneate, apex acuminate; usually 3 - lobed, rarely 5 - lobed or unlobed; margins irregularly double-serrate above the middle part; venation craspedodromous; glabrous adaxially, except for the loosely hairy midrib, pinnate veins slightly impressed above, prominent below, veins entering the tip of the serrations. Inflorescences corymb, 7–18 flowered, 4 cm long, 8 cm wide; pedicels and peduncles white-pubescent; bracts linear-lanceolate 2–3 mm long, margin glandular-serrate, caducous; hypanthium externally white-pubescent; small flower 2 cm in diameter; petals suborbicular, white, about 5 mm long, very shortly clawed; sepals triangular, apex caudate-acuminate, 4–6 mm long, nearly as long as the calyx tube, white-pubescent adaxially; stamens 20; styles 5, base white-villous. Fruits globose, 10–15 mm in diameter, red, glabrous; sepals persistent, reflexed; nutlets 5, flat on both sides, grooved on the back. Distribution. China (Shandong: Mount Tai). Conservation status. Crataegus shandongensis is currently known from a single extant population situated along the slope of Mount Tai. Despite thorough field observations over the past 38 years by one of the authors (Wei-Dong Peng), no additional populations have been found. Although Mount Tai has been under continuous protection for over 5,000 years due to its profound cultural significance, which has helped to preserve the natural habitat to some extent, the species remains restricted to this limited area. According to the IUCN Red List Criteria (IUCN 2022), specifically criteria B 1 ab (iii) + 2 ab (iii), C. Shandongensis meets the thresholds for Critically Endangered (CR) status. These criteria pertain to the restricted geographic range (criterion B 1) and the limited area of occupancy (criterion B 2), coupled with an ongoing decline in habitat quality (subcriterion ab (iii)). The restricted distribution and the absence of additional populations justify the classification of C. shandongensis as CR. Additional specimens examined (paratypes). China. Shandong, Mount Tai (Taishan), altitude 700–800 m, 2 July 1984, W. D. Peng 84001 (PE [barcode 01153320!, Fig. 5 D], LBG [barcode 00021556!, Fig. 5 E], SDAU! [Fig. 5 F]).